javascript纪录

2019年8月31日 169次阅读来源: 苏生不惑

纪录毛病日记

window.onerror = function(message, url, lineNumber,columnNo,error) {
    var data = {
        'message':message,
        'url':url,
        'error':error.stack
    };
    $.ajax({
        url:"/error/capture",
        type:'post',
        data:data,
        success:function(){
 
        }
    });
    return true;
};

javascript随机数天生算法

function rnd( seed ){
    seed = ( seed * 9301 + 49297 ) % 233280; //为什么运用这三个数?
    return seed / ( 233280.0 );
};

function rand(number){
    today = new Date(); 
    seed = today.getTime();
    return Math.ceil( rnd( seed ) * number );
};

myNum=(rand(5)); 

var rand = (function(){
  var seed = (new Date()).getTime()
  function r(){
    seed = (seed*9301+49297)%233280
    return seed/(233280.0)
  }
  return function(number){
    return Math.ceil(r()*number)
  }
})()

rand = (function(){
  var today = new Date(); 
  var seed = today.getTime();
  function rnd(){
    seed = ( seed * 9301 + 49297 ) % 233280;
    return seed / ( 233280.0 );
  };
  return function rand(number){
    // return Math.ceil(rnd(seed) * number);
    return Math.ceil(rnd() * number);
  };
})();
myNum = (rand(5));

JavaScript 中，怎样求出两个数组的交集和差集

_.intersection([1, 2, 3], [101, 2, 1, 10], [2, 1]);
=> [1, 2]
_.difference([1, 2, 3, 4, 5], [5, 2, 10]);
=> [1, 3, 4]
let a = new Set([1, 2, 3]);
let b = new Set([3, 5, 2]); 

// 并集
let unionSet = new Set([...a, ...b]);
//[1,2,3,5]

// 交集
let intersectionSet = new Set([...a].filter(x => b.has(x)));
// [2,3]

// ab差集
let differenceABSet = new Set([...a].filter(x => !b.has(x)));
// [1]

再把Set转换为数组即可.
let arr = Array.from(set);
// 或 let arr = [...set];


雷同的

a.filter(function(v){ return b.indexOf(v) > -1 })
差别的
a.filter(function(v){ return !(b.indexOf(v) > -1) }).concat(b.filter(function(v){ return !(a.indexOf(v) > -1)}))

猎取某个DOM元素绑定的事宜

getEventListeners($('selector')) 要领以数组对象的花样返回某个元素绑定的一切事宜
getEventListeners($('#firstName')).click[0].listener 会返回ID为 firstName 元素绑定的click事宜

inspect($('selector')) 会搜检一切婚配挑选器的DOM元素，并返回一切挑选器挑选的DOM对象。比方inspect($('#firstName')) 挑选一切ID是 firstName 的元素，inspect($('a')[3]) 搜检并返回页面上第四个 p元素。
$0, $1, $2等等会返回你近来搜检过的几个元素，比方 $0 会返回你末了搜检的元素，$1 则返回倒数第二个

《javascript纪录》

img onerror事宜触发


$('img').each(function() {
    if (!this.complete || typeof this.naturalWidth == "undefined" || this.naturalWidth == 0) {
        this.src = 'default.png';
    }
});

制止浏览器记着暗码

在input[type=’password’]的前面加上一个隐蔽的暗码框即可,且要求是：不能增加id和name属性
<input type=’password’ style=’display:none;’ />

经由过程 js 修正微信浏览器的title

var $body = $('body');
document.title = ‘title’
// hack在微信等webview中没法修正document.title的状况
var $iframe = $('<iframe src="/favicon.ico"></iframe>').on('load', function() {
setTimeout(function() {
$iframe.off('load').remove()
}, 0)
}).appendTo($body)

图片的预加载

function imgLoad(src){
    var img = new Image();
    if(img.complete){ //从缓存内里取
        callback();
    }else{
        img.onload = function(){ //现实加载完成
            callback();
        }
    }
    img.src = src;
}

完成类似于add(1)(2)(3)挪用

function add(x){
    var sum = x;
    var tmp = function(y){
        sum = sum + y;
        return tmp;     
    }
    tmp.toString = function(){
        return sum;
    }
    return tmp
}

用代码来画个国旗

<html>
<head>
<script>
var col=new Array("red","brown");
var ticker=0;
var step=0;
function drawBackground(){
var g=document.getElementById("background").getContext("2d");
var grd=g.createLinearGradient(-560+ticker, 0, 1400+ticker,0);
for (var i=0; i<10; i++)
grd.addColorStop(i/10,col[(i + step)%col.length]);
ticker=ticker+10;
if (ticker>=196){
    ticker=0;
    step++;
    }
g.fillStyle=grd;
g.fillRect(0,0,1600,700);
}

function preperation(){
    setInterval('drawBackground()',100);
  }
</script>
<style type="text/css">
#myCanvas{
 z-index:2;    
 position:absolute; left:0px; top:-5px;
}
#background{
    z-index:1;
    position:absolute;
    left:0px;
    top:0px;
}
</style>
</head>
<body onLoad="preperation()">
<canvas id="myCanvas" width="900" height="600" >
Your browser does not support the HTML5 canvas tag.
</canvas>
<canvas id="background" width="1600" height="700" ></canvas>
<script>
var x=new Array(0,12,54,18,28,0,-28,-18,-54,-12,0);    //五角星样品坐标xx数组
var y=new Array(-53,-17,-17,1,45,19,45,1,-17,-17,-53); //五角星样品坐标y数组

var c=document.getElementById("myCanvas");
var ctx=c.getContext("2d"); //获得画笔
//样品数组x轴坐标 a , 和y轴坐标 b
//指定位置[locationX,locationY]
//实在五角星的大小，与样品五角星尺寸之比 f
//五角星画完后，扭转的角度 rotation
function star(a,b,locationX,locationY,f,rotation){
ctx.save();//纪录绘图（画笔）的初始环境
ctx.translate(locationX,locationY);
ctx.rotate(rotation*Math.PI/180.0);
ctx.beginPath();
ctx.moveTo(Math.round(a[0]*f),Math.round(b[0]*f));
for (var i=1;i<a.length;i++)
ctx.lineTo(Math.round(a[i]*f),Math.round(b[i]*f));
ctx.closePath();
ctx.fillStyle="yellow";
ctx.fill();
ctx.restore();//复原绘图（画笔）的初始环境
}
star(x,y,165,165,1.4,0);//画大五角星
star(x,y,301,65,0.5,30);//画小五角星
star(x,y,362,126,0.5,-30);//画小五角星
star(x,y,359,216,0.5,0);//画小五角星
star(x,y,301,273,0.5,30);//画小五角星
</script>
</body>
</html>

js猎取URL中的参数

function getQueryString(url, name) {
    var reg = new RegExp("(^|&|\\?)" + name + "=([^&]*)(&|$)", "i");
    var r = url.substr(1).match(reg);
    if (r != null) return unescape(r[2]); return null;
}

视频video标签在挪动端的播放总结

function video_loading( $video ){
        $('.video_loading').show();

        var timer = setInterval(function(){
            var currentTime = $video[0].currentTime; // 检测当前的播放时刻

            if( currentTime>0 ){
                $('.video_loading').hide();
                clearInterval( timer );
            }
        }, 100)
    }
    /**
        视频的播放时刻转变时举行的操纵
        videoid video标签的id
        cur 当前播放时刻，能够传入ended参数
        func 回调函数
    */
    videoUpdate : function(videoid, cur, func){
        var myVideo = document.getElementById(videoid);

        if( myVideo ){
            if( typeof cur =='number' ){
                myVideo.addEventListener('timeupdate', function(){
                    if( this.currentTime>=cur ){
                        func();
                        myVideo.removeEventListener('timeupdate', function(){

                        }, false);
                    }
                }, false);
            }else{
                myVideo.addEventListener(cur, function(){
                    func();
                }, false);
            }
        }
    }
    // 第一屏的视频举行到4秒时，显现通明图层以供应用户操纵
    tool.videoUpdate( 'video1', 4, function(){
        $('.s1 .overlay').show();
    });

    // 第一屏的视频完毕时，显现向下滑动提醒按钮
    tool.videoUpdate( 'video1', 'ended', function(){
        $('.s1 .tip').show();
    });

为博客的文章增加二维码


$('.bcontent').append('<div class="qrcode"><a href="javascript:;">点击天生二维码，可在手机端寓目</a><div class="tsp"></div></div>');
$('.bcontent').on('click', '.qrcode a', function(){
    var $tsp = $(this).next();

    if( $tsp.find('canvas').length ){
        if( $tsp.css('display')=='block' ){
            $tsp.hide();
        }else{
            $tsp.show();
        }
    }else{
        if( self.showing ){
            return;
        }
        self.showing = true;
        $tsp.show().html( '正在天生中...' );
        $.ajax({
            url : 'jquery.qrcode.min.js',
            dataType : 'script',
            type : 'get'
        }).done(function(){
            self.showing = false;
            $tsp.html('');
            $tsp.qrcode({
                render : 'canvas',
                width : 176,
                height: 176,
                text : window.location.href
            });
        })
    }
})

运用DOM中的a标签剖析url

// 建立一个分外的a标签
function parseURL(url) {
    var a =  document.createElement('a');
    a.href = url;
    return {
        source: url,
        protocol: a.protocol.replace(':',''),
        host: a.hostname,
        port: a.port,
        query: a.search,
        params: (function(){
            var ret = {},
                seg = a.search.replace(/^\?/,'').split('&'),
                len = seg.length, i = 0, s;
            for (;i<len;i++) {
                if (!seg[i]) { continue; }
                s = seg[i].split('=');
                ret[s[0]] = s[1];
            }
            return ret;
        })(),
        file: (a.pathname.match(/\/([^\/?#]+)$/i) || [,''])[1],
        hash: a.hash.replace('#',''),
        path: a.pathname.replace(/^([^\/])/,'/$1'),
        relative: (a.href.match(/tps?:\/\/[^\/]+(.+)/) || [,''])[1],
        segments: a.pathname.replace(/^\//,'').split('/')
    };
}
var myURL = parseURL('http://abc.com:8080/dir/index.html?id=255&m=hello#top');
 
myURL.file;     // 'index.html'
myURL.hash;     // 'top'
myURL.host;     // 'abc.com'
myURL.query;    // '?id=255&m=hello'
myURL.params;   // Object = { id: 255, m: hello }
myURL.path;     // '/dir/index.html'
myURL.segments; // Array = ['dir', 'index.html']
myURL.port;     // '8080'
myURL.protocol; // 'http'
myURL.source;   // 'http://abc.com:8080/dir/index.html?id=255&m=hello#top'

javascript怎样增加前置0

function addPreZero(num){
    return ('000000000'+num).slice(-10);
}

html5完成图片预览和检察原图

<input type="file" id='upimg' />
var upimg = document.querySelector('#upimg');
upimg.addEventListener('change', function(e){
    var files = this.files;
    if(files.length){
        // 对文件举行处置惩罚，下面会解说checkFile()会做什么
        checkFile(this.files);
    }
});
// 图片处置惩罚
function checkFile(files){
    var file = files[0];
    var reader = new FileReader();
    // show示意<div id='show'></div>，用来展现图片预览的
    if(!/image\/\w+/.test(file.type)){
        show.innerHTML = "请确保文件为图象范例";
        return false;
    }
    // onload是异步操纵
    reader.onload = function(e){
        show.innerHTML = '<img src="'+e.target.result+'" alt="img">';
    }
    reader.readAsDataURL(file);
}

挪动端在页面输出调试信息

function log(){
    try{
        throw new Error();
    }catch(e){
        console.log(e.stack);
    }
}
log();
function log(msg){
    var $body = document.querySelector('body');
    
    if( !$body.querySelector('.info_wz_852') ){
        $body.innerHTML += '<div class="info_wz_852" style="position:fixed;top:0;left:0;z-index:99999; background:#000;color:#f00;"></div>';
    }
        
    var $info = $body.querySelector('.info_wz_852');
    var date = new Date(),
        minute = ('00'+date.getMinutes()).slice(-2),
        second = ('00'+date.getSeconds()).slice(-2);
    
    try{
        throw new Error();
    }catch(e){
        var loc = (e.stack.replace(/Error\n/).split(/\n/)[1]).replace(/^(\s|\u00A0)+/,'').replace(/(\s|\u00A0)+$/,'');
            
        // var arr = loc.split(':'),
        //     col = parseInt(arr.pop()),
        //     line = parseInt(arr.pop());
    
        $info.innerHTML += '<p>['+minute+':'+second+'] '+loc+'</p><p>'+msg+'</p><br/>';
    }
}

推断 x 是不是是整数

function isInteger(x) { 
    return parseInt(x, 10) === x; 
}
function add(x, y) {
    return x.toPrecision() + y.toPrecision()
}
console.log(add(0.1,0.2));
function add(num1, num2){
  let r1, r2, m;
  r1 = (''+num1).split('.')[1].length;
  r2 = (''+num2).split('.')[1].length;

  m = Math.pow(10,Math.max(r1,r2));
  return (num1 * m + num2 * m) / m;
}
console.log(add(0.1,0.2));   //0.3
console.log(add(0.15,0.2256)); //0.3756

PhantomJS抓取网页并将它渲染成图片

var page = require('webpage').create();
page.settings.userAgent = 'WebKit/534.46 Mobile/9A405 Safari/7534.48.3';
page.settings.viewportSize = { width: 400, height: 600 };
page.open('http://m.bbc.co.uk/news/business', function (status) {
    if (status !== 'success') {
        console.log('Unable to load BBC!');
        phantom.exit();
    } else {
        window.setTimeout(function () {
            page.clipRect = { left: 0, top: 0, width: 400, height: 600 };
            page.render('bbc-page1.png');
            page.clipRect = { left: 0, top: 600, width: 400, height: 600 };
            page.render('bbc-page2.png');
            phantom.exit();
        }, 2000);
    }
});

复制与粘贴


<p>Email me at <a class="js-emaillink" href="mailto:matt@example.co.uk">matt@example.co.uk</a></p>
<p><button class="js-emailcopybtn"><img src="./images/copy-icon.png" /></button></p>
var copyEmailBtn = document.querySelector('.js-emailcopybtn');
copyEmailBtn.addEventListener('click', function(event) {
    // Select the email link anchor text
    var emailLink = document.querySelector('.js-emaillink');
    var range = document.createRange();
    range.selectNode(emailLink);
    window.getSelection().addRange(range);

    try {
        // Now that we've selected the anchor text, execute the copy command
        var successful = document.execCommand('copy');
        var msg = successful ? 'successful' : 'unsuccessful';
        console.log('Copy email command was ' + msg);
    } catch(err) {
        console.log('Oops, unable to copy');
    }

    // Remove the selections - NOTE: Should use
    // removeRange(range) when it is supported
    window.getSelection().removeAllRanges();
});

倒计时的JS

 

var time_distance;
var totleTime;
var stop;
function countdownTime(disTime){
    time_distance =disTime;
    totleTime=time_distance;
    showTime();
}
function showTime(){
    time_distance=totleTime;
    var day=0,
    hour=0,
    minute=0,
    second=0;//时刻默认值
    if(time_distance > 0){
        day = Math.floor(time_distance / (60 * 60 * 24*1000));
        hour = Math.floor(time_distance / (60 * 60*1000)) - (day * 24);
        minute = Math.floor(time_distance / (60*1000)) - (day * 24 * 60) - (hour * 60);
        second = Math.floor(time_distance/1000) - (day * 24 * 60 * 60) - (hour * 60 * 60) - (minute * 60);
    }
    if (hour <= 9) hour = '0' + hour;
    if (minute <= 9) minute = '0' + minute;
    if (second <= 9) second = '0' + second;
    // 显现时刻 
    $("#time_d").text(day+'天');
    $("#time_h").text(hour+'时'); 
    $("#time_m").text(minute+'分'); 
    $("#time_s").text(second+'秒');
    stop=setTimeout("showTime()",1000);
    totleTime=totleTime-1000;
    if(totleTime<1000){
        $("#time_d").text('运动');
        $("#time_h").text('已'); 
        $("#time_m").text('完毕'); 
        $("#time_s").text('。');
        clearTimeout(stop);
        }
    
}

一个数每隔一秒实行加1并打印出来

var count = (function() {
    var timer;
    var i = 0;
    function change(tar) {
        i++;
        console.log(i);
        if (i === tar) {
            clearTimeout(timer);
            return false;
        }
        timer = setTimeout(function() {
            change(tar)
        }, 1000)

    }
    return change;
})()

count(50)

onerror log

'use strict';
function errorHandler( message, source, lineno, colno, error){
    var errorDiv = document.getElementById("error");
    errorDiv.classList.remove("hide");
    console.log("Error happened, message:", message);
    console.log("On source file: ", source);
    console.log("On line - col: ", lineno, "-", colno);
    console.log("Error:", error);
    try {
        var ua = navigator.userAgent;
        console.log("UA: ", ua);
    } catch (e) {
        console.log("Unable to get UA");
    }
}
window.onerror = errorHandler;

javascript copy

<div class="line copyAsText">
                <label for="bbcode" class="copyBtn">BBCode</label>
                <input name="bbcode" value="[img]http://7sdream-rikka-demo.daoapp.io/files/95356e2f-7648-431f-8fe3-754d833d6cc1.png[/img]" disabled/>
            </div>
'use strict';
function addCopyEventListener(url){
    var divs = document.querySelectorAll("div.copyAsText");
    for (var index in divs) {
        if(!divs.hasOwnProperty(index)) {
            continue;
        }
        var div = divs[index];
        var input = div.querySelector("input");
        var btn = div.querySelector("label");
        if (url !== "") {
            var template = input.getAttribute("data-template");
            input.value = template.replace("${url}", url);
        }
        void function(btn, input){
            btn.addEventListener("click", function(){
                if (btn.disabled) {
                    return;
                }
                var res = false;
                try {
                    input.disabled = false;
                    var section = window.getSelection();
                    section.removeAllRanges();
                    input.focus();
                    input.setSelectionRange(0, input.value.length);
                    res = document.execCommand("copy");
                    input.disabled = true
                } catch(e) {
                    res = false;
                }
                if (res) {
                    var origin = btn.textContent;
                    btn.textContent = "Copied!";
                    btn.disabled = true;
                    setTimeout(function(){
                        btn.textContent = origin;
                        btn.disabled = false;
                    }, 2000);
                } else {
                    window.prompt("Copy to clipboard: Ctrl+C, Enter", input.value);
                }
            });
        }(btn, input);
    }
}
addCopyEventListener("");
//https://github.com/imsobear/blog/issues/31
//只需要对相应的元素绑定 mouseenter 的事宜，然后相应 selectText() 这个要领就 ok
function selectText (element) {
    var text = element,
        range,
        selection;

    if (body.createTextRange) {
        // IE
        range = body.createTextRange();
        range.moveToElementText(text);
        range.select();
    } else if (window.getSelection) {
        // Others
        selection = window.getSelection();
        range = doc.createRange();
        range.selectNodeContents(text);
        selection.removeAllRanges();
        selection.addRange(range);
    } else {
        return false;
    }
}

把节点列表(NodeList)转换为数组

var elements = document.querySelectorAll("p"); // NodeList
var arrayElements = [].slice.call(elements); // 如今 NodeList 是一个数组
var arrayElements = Array.from(elements); // 这是另一种转换 NodeList 到 Array  的要领

var array1 = [1,2,3];
var array2 = [4,5,6];
console.log(array1.push.apply(array1, array2)); // [1,2,3,4,5,6];

JavaScript完成字符串长度截取

 

function cutstr(str, len) {
        var temp;
        var icount = 0;
        var patrn = /[^\x00-\xff]/;
        var strre = "";
        for (var i = 0; i < str.length; i++) {
            if (icount < len - 1) {
                temp = str.substr(i, 1);
                if (patrn.exec(temp) == null) {
                    icount = icount + 1
                } else {
                    icount = icount + 2
                }
                strre += temp
            } else {
                break
            }
        }
        return strre + "..."
    }
    function $(id) {
        return !id ? null : document.getElementById(id);
    }
  // 用法：假如地点是 test.htm?t1=1&t2=2&t3=3, 那末能获得：GET["t1"], GET["t2"], GET["t3"]
function get_get(){ 
  querystr = window.location.href.split("?")
  if(querystr[1]){
    GETs = querystr[1].split("&")
    GET =new Array()
    for(i=0;i<GETs.length;i++){
      tmp_arr = GETs[i].split("=")
      key=tmp_arr[0]
      GET[key] = tmp_arr[1]
    }
  }
  return querystr[1];
}

/**
 * 推断变量是不是空值
 * undefined, null, '', false, 0, [], {} 均返回true，不然返回false
 */
function empty(v){
    switch (typeof v){
        case 'undefined' : return true;
        case 'string'    : if(trim(v).length == 0) return true; break;
        case 'boolean'   : if(!v) return true; break;
        case 'number'    : if(0 === v) return true; break;
        case 'object'    : 
            if(null === v) return true;
            if(undefined !== v.length && v.length==0) return true;
            for(var k in v){return false;} return true;
            break;
    }
    return false;
}

function backTop(btnId) {
    var btn = document.getElementById(btnId);
    var d = document.documentElement;
    var b = document.body;
    window.onscroll = set;
    btn.style.display = "none";
    btn.onclick = function() {
        btn.style.display = "none";
        window.onscroll = null;
        this.timer = setInterval(function() {
            d.scrollTop -= Math.ceil((d.scrollTop + b.scrollTop) * 0.1);
            b.scrollTop -= Math.ceil((d.scrollTop + b.scrollTop) * 0.1);
            if ((d.scrollTop + b.scrollTop) == 0) clearInterval(btn.timer, window.onscroll = set);
        },
        10);
    };
    function set() {
        btn.style.display = (d.scrollTop + b.scrollTop > 100) ? 'block': "none"
    }
};
backTop('goTop');

mockjs让前端开辟独立于后端

    
<script src="http://mockjs.com/dist/mock.js"></script>

<script>
  //挪用mock要领模仿数据
  Mock.mock('http://laoyu', {
    "errorcode": 0,//0示意胜利，1示意毛病
    "message": "xx信息不完整", //弹出毛病信息
  });
  //运用ajax举行测试
var xhr = XMLHttpRequest();
xhr.open("post","http://laoyu",true);
xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xhr.send(null);
xhr.onreadystatechange = function(){
    if(xhr.readyState == 4){
        if((xhr.status>=200 && xhr.status<300) || xhr.status== 304){
            var data = JSON.parse(xhr.responseText);  
            //由于reponseText返回的是字符串，将字符串转换成我们想要的JSON数据，如许就能够挪用了
            console.log(data)；  //在掌握台中打印出返回的内容
        }else{
            alert("Request was unsuccessful: " + xhr.status);
        }
    }
}
  </script>

rand num


function GetRandomNum(Min,Max)
{   
    var Range = Max - Min;   
    var Rand = Math.random();   
    return(Min + Math.round(Rand * Range));   
}   
var num = GetRandomNum(10,100);

建立XMLHttpRequest对象

function createXHR(){
    if(typeof XMLHttpRequest != "undefined"){
        return new XMLHttpRequest();
    }else if(typeof ActiveXObject != "undefined"){
        if(typeof arguments.callee.activeXString != "string"){
            var versions = ["MSXML2.XMLHttp.6.0","MSXML2.XMLHttp.                       3.0","MSXML2.XMLHttp"],i,len;
            for(i = 0,len=versions.length;i<len;i++){
                try{
                    new ActiveXObject(versions[i]);
                    arguments.callee.activeXString = versions[i];
                    break;
                }catch(ex){
                    //跳过
                }
            }
        }
        return new ActiveXObject(arguments.callee.activeXString);
    }else{
        throw new Error("No XHR object available.");
    }
}
var xhr = createXHR();
xhr.open("post","check.php",true);
xhr.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xhr.send(null);
xhr.onreadystatechange = function(){
    if(xhr.readyState == 4){
        if((xhr.status>=200 && xhr.status<300) || xhr.status== 304){
            alert(xhr.responseText);
        }else{
            alert("Request was unsuccessful: " + xhr.status);
        }
    }
}

多行文本溢出显现省略号

var module = document.getElementById(“clamp-this-module”);
$clamp(module, {clamp: 3});

微信页面监听摇一摇事宜，并伴有音效

<audio style="display: none;" src="http://xunlei.sc.chinaz.com/files/download/sound1/201410/5018.mp3" id="musicBox" preload="preload"  controls></audio>
<script>
    var SHAKE_THRESHOLD = 3000;    
    var last_update = 0;    
    var x=y=z=last_x=last_y=last_z=0;   
var  media; 
media= document.getElementById("musicBox");
function init(){
       last_update=new Date().getTime();
        if (window.DeviceMotionEvent) { 
            window.addEventListener('devicemotion',deviceMotionHandler, false);  
        } else{    
alert('not support mobile event');
}
}
    function deviceMotionHandler(eventData) {    
    var acceleration =eventData.accelerationIncludingGravity; 
    var curTime = new Date().getTime(); 
    if ((curTime - last_update)> 100) {  
            var diffTime = curTime -last_update;    
            last_update = curTime;        
            x = acceleration.x; 
            y = acceleration.y;   
            z = acceleration.z;   
            var speed = Math.abs(x +y + z - last_x - last_y - last_z) / 
    diffTime * 10000;     
            if (speed > SHAKE_THRESHOLD) {    
                media.play();
            }    
            last_x = x;    
            last_y = y;    
            last_z = z;    
        }
    }
    window.onload = function(){
        init();
    }
</script>

鼠标向下转动的时刻header会消逝

//设置下css，加个绿色的背景，显著
$('.sf-header').css({
    background : '#CFC',
    width: '100%'
});

//
$(document).scroll( function(){
    var me = arguments.callee; //匿名函数能够 经由过程 arguments.callee 挪用本身
    me.doc = me.doc || $(document); //缓存 $(document);
    me.head = me.head || $('.sf-header');
    me.lastTop = me.lastTop || me.doc.scrollTop();
    if( me.doc.scrollTop() < 20 ||  me.doc.scrollTop() > me.lastTop ){
        //向下 或再 页面顶部，放在 头部
        me.head.css({ position : 'relative' });
    }else if( me.doc.scrollTop() < me.lastTop  ){
        //向上，悬浮
        me.head.css({ position : 'fixed' });
    }
    me.lastTop = me.doc.scrollTop();
});

v2ex 的下一主题

window.location.href = 'https://www.v2ex.com/t/' + (Number(document.location.href.replace(/https:\/\/www\.v2ex\.com\/t\/(\d?)/i, '$1'))+1)
window.location.href.substring(23,29) * 1 + 1
location.href=location.href.split(/[/#]/)[4]*1+1 
location.pathname.substring(3)

推断一个单词是不是是回文

function checkPalindrom(str) {  
    return str == str.split('').reverse().join('');
}

去掉一组整型数组反复的值

let unique = function(arr) {  
  let hashTable = {};
  let data = [];
  for(let i=0,l=arr.length;i<l;i++) {
    if(!hashTable[arr[i]]) {
      hashTable[arr[i]] = true;
      data.push(arr[i]);
    }
  }
  return data

}

统计一个字符串涌现最多的字母

function findMaxDuplicateChar(str) {  
  if(str.length == 1) {
    return str;
  }
  let charObj = {};
  for(let i=0;i<str.length;i++) {
    if(!charObj[str.charAt(i)]) {
      charObj[str.charAt(i)] = 1;
    }else{
      charObj[str.charAt(i)] += 1;
    }
  }
  let maxChar = '',
      maxValue = 1;
  for(var k in charObj) {
    if(charObj[k] >= maxValue) {
      maxChar = k;
      maxValue = charObj[k];
    }
  }
  return maxChar;

}

天生斐波那契数组

function getFibonacci(n) {  
  var fibarr = [];
  var i = 0;
  while(i<n) {
    if(i<=1) {
      fibarr.push(i);
    }else{
      fibarr.push(fibarr[i-1] + fibarr[i-2])
    }
    i++;
  }

  return fibarr;
}

闭包



var myObject = {
    foo: "bar",
    func: function() {
        var self = this;
        console.log("outer func:  this.foo = " + this.foo);
        console.log("outer func:  self.foo = " + self.foo);
        (function(test) {
            console.log("inner func:  this.foo = " + test.foo);  //'bar'
            console.log("inner func:  self.foo = " + self.foo);
     }(self));
    }
};
myObject.func();

for(var i = 0; i < 5; i++) {
    setTimeout(function() {
        console.log(i);  // 555555
    }, 1000);
}
for(var i = 0; i < 5; i++) {
    (function(i) {
      setTimeout(function() {
        console.log(i);  //0 ， 1 ， 2 ， 3 ， 4 
      }, 1000);
    })(i)
}
function add(num1, num2){
  let r1, r2, m;
  r1 = (''+num1).split('.')[1].length;
  r2 = (''+num2).split('.')[1].length;

  m = Math.pow(10,Math.max(r1,r2));
  return (num1 * m + num2 * m) / m;
}
console.log(add(0.1,0.2));   //0.3
console.log(add(0.15,0.2256)); //0.3756

10 的阶乘

console.log((function f(n){return ((n > 1) ? n * f(n-1) : n)})(10));

逻辑与返回第一个是 false 的操纵数或许末了一个是 true 的操纵数

假如某个操纵数为 false ，则该操纵数以后的操纵数都不会被盘算
console.log(1 && 2 && 0); //0
console.log(1 && 0 && 1); //0
console.log(1 && 2 && 3); //3

逻辑或返回第一个是 true 的操纵数或许末了一个是 false 的操纵数
console.log(1 || 2 || 0); //1
console.log(0 || 2 || 1); //2
console.log(0 || 0 || false); //false

假如某个操纵数为 true ，则该操纵数以后的操纵数都不会被盘算
假如逻辑与和逻辑或作夹杂运算，则逻辑与的优先级高
if 中，[] 和 {} 都表现为 true

Unicode 编码转换

function encodeUTF8(str){
    var temp = "",rs = "";
    for( var i=0 , len = str.length; i < len; i++ ){
        temp = str.charCodeAt(i).toString(16);
        rs  += "\\u"+ new Array(5-temp.length).join("0") + temp;
    }
    return rs;
 }
 function decodeUTF8(str){
    return str.replace(/(\\u)(\w{4}|\w{2})/gi, function($0,$1,$2){
        return String.fromCharCode(parseInt($2,16));
    }); 
 } 
encodeUTF8('中文')
"\u4e2d\u6587"
decodeUTF8('\u4e2d\u6587')
"中文"
//https://segmentfault.com/q/1010000000095710
var decToHex = function(str) {
    var res=[];
    for(var i=0;i < str.length;i++)
        res[i]=("00"+str.charCodeAt(i).toString(16)).slice(-4);
    return "\\u"+res.join("\\u");
}

var hexToDec = function(str) {
    str=str.replace(/\\/g,"%");
    return unescape(str);
}
var decodeHtmlEntity = function(str) {
  return str.replace(/&#(\d+);/g, function(match, dec) {
    return String.fromCharCode(dec);
  });
};
var str = 'JavaScript&#39640;&#32423;&#31243;&#24207;&#35774;&#35745;';
console.log(decodeHtmlEntity(str));//JavaScript高等程序设计
var encodeHtmlEntity = function(str) {
  var buf = [];
  for (var i=str.length-1;i>=0;i--) {
    buf.unshift(['&#', str[i].charCodeAt(), ';'].join(''));
  }
  return buf.join('');
};
var str = '高等程序设计';
console.log(encodeHtmlEntity(str));//&#39640;&#32423;&#31243;&#24207;&#35774;&#35745;

function u2str(text){ 
     return $('<p></p>').html(text).text();
}

数组反转

var test = [
  [1, 0, 4, 3, 2],
  [0, 4, 3, 2, 1],
  [4, 3, 2, 1, 0],
  [3, 2, 1, 0, 4]
];

test.forEach(arr => console.log(reversal(arr)));

// 反转
function reversal(arr) {
  let len = arr.length;
  // get max
  let max = arr[0];
  let index = 0;
  arr.forEach((v, i) => {
    if (v <= max) return;
    max = v;
    index = i;
  });

  // strat re
  let tmp = arr.reverse().concat(arr, arr);
  let newIndex = len - 1 - index + len;

  return tmp.slice(newIndex - index, newIndex + len - index);
}
var arr = [1, 0, 4, 3, 2];
反转为
var arr = [2, 3, 4, 0, 1];

chrome console

dir($(‘selector’)) 会返回婚配挑选器的DOM元素的一切属性
猎取某个DOM元素绑定的事宜 getEventListeners($(‘#firstName’)).click[0].listener