开发中常用的JS知识点集锦

索引

1、对象深拷贝

2、网络图片转base64, 在线图片点击下载

3、对象深拷贝

4、对象深拷贝

5、对象深拷贝

6、对象深拷贝

1、对象的深拷贝(一级属性拷贝和多级属性嵌套拷贝)

//深拷贝函数(满足属性多级嵌套)
function deepCloneObj(sourceObj){ var obj = (sourceObj instanceof Array) ? [] : {}; for (var key in sourceObj){ var tmp = sourceObj[key]; //处理重复引用,防止死循环
        if (tmp === sourceObj){ continue; 
        } if (typeof tmp === 'object'){
            obj[key] = arguments.callee(tmp); //属性为对象,递归深度复制
 } else{
            obj[key] = tmp;
        }
    } return obj;
} //

1、测试对象的深拷贝

var obj = {info:{name:'大锤'}, sign: 'xxx'}; var obj2 = Object.assign({}, obj);  //一级属性深拷贝 (es6的Object.assign函数特性)
var obj3 = {...obj};            //一级属性深拷贝 (es6扩展运算符)
var obj4 =  deepCloneObj(obj);  //递归深拷贝所有层级属性
var obj5 = JSON.parse(JSON.stringify(obj)); //深拷贝所有层级属性
 console.log('obj: ', JSON.stringify(obj));
console.log('obj2: ', JSON.stringify(obj2));
console.log('obj3: ', JSON.stringify(obj3));
console.log('obj4: ', JSON.stringify(obj4));
console.log('obj5: ', JSON.stringify(obj5));
console.log(".........end..........");

setTimeout(function(){

    obj.sign = 'a**b'; 
    obj.info.name = '一二三';
    console.log('\n****update info ****');
    console.log('obj: ', JSON.stringify(obj));
    console.log('obj2: ', JSON.stringify(obj2));
    console.log('obj3: ', JSON.stringify(obj3));
    console.log('obj4: ', JSON.stringify(obj4));
    console.log('obj5: ', JSON.stringify(obj5));
    console.log(".........end..........");
},100); /* 打印日志结果:
obj:  {"info":{"name":"大锤"},"sign":"xxx"}
obj2:  {"info":{"name":"大锤"},"sign":"xxx"}
obj3:  {"info":{"name":"大锤"},"sign":"xxx"}
obj4:  {"info":{"name":"大锤"},"sign":"xxx"}
obj5:  {"info":{"name":"大锤"},"sign":"xxx"}
.........end..........

****update info ****
obj:  {"info":{"name":"一二三"},"sign":"a**b"}   //只拷贝了第一级属性
obj2:  {"info":{"name":"一二三"},"sign":"xxx"}   //只拷贝了第一级属性
obj3:  {"info":{"name":"一二三"},"sign":"xxx"}   //只拷贝了第一级属性
obj4:  {"info":{"name":"大锤"},"sign":"xxx"}     //所有层级深拷贝
obj5:  {"info":{"name":"大锤"},"sign":"xxx"}    //所有层级深拷贝 */

//2、测试数组的深拷贝

setTimeout(function(){
    console.log('\n\n.....数组的深拷贝测试....'); var arr = [{name: '小明'}, true, 18]; var arr2 = Object.assign([], arr); var arr3 = [...arr2]; var arr4 = deepCloneObj(arr); var arr5 = JSON.parse(JSON.stringify(arr));

    console.log('arr: ', JSON.stringify(arr));
    console.log('arr2: ', JSON.stringify(arr2));
    console.log('arr3: ', JSON.stringify(arr3));
    console.log('arr4: ', JSON.stringify(arr4));
    console.log('arr5: ', JSON.stringify(arr5));
    console.log("......end......\n");

    setTimeout(function(){

        arr[0].name = '五六七', arr[1] = false, arr[2] = 99;
        console.log('arr: ', JSON.stringify(arr));
        console.log('arr2: ', JSON.stringify(arr2));
        console.log('arr3: ', JSON.stringify(arr3));
        console.log('arr4: ', JSON.stringify(arr4));
        console.log('arr5: ', JSON.stringify(arr5));

    }, 100); /* 数组测试打印日志结果:
    .....数组的深拷贝测试....
    arr:  [{"name":"小明"},true,18]
    arr2:  [{"name":"小明"},true,18]
    arr3:  [{"name":"小明"},true,18]
    arr4:  [{"name":"小明"},true,18]
    arr5:  [{"name":"小明"},true,18]
    ......end......

    arr:  [{"name":"五六七"},false,99]
    arr2:  [{"name":"五六七"},true,18]    //只拷贝了第一级属性
    arr3:  [{"name":"五六七"},true,18]   //只拷贝了第一级属性
    arr4:  [{"name":"小明"},true,18]    //所有层级深拷贝
    arr5:  [{"name":"小明"},true,18]   //所有层级深拷贝 */ },1000);</pre>
    原文作者:前端爱好者
    原文地址: https://segmentfault.com/a/1190000017081003
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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