JavaScript一切关键字
break
case
catch
continue
default
delete
do
else
finally
for
function
if
in
instanceof
new
return
switch
this
throw
try
typeof
var
void
while
delete
:删除对象的某个属性
function obj(id,name){
this.id = id;
this.name = name;
this.getName = function(){
return this.name;
}
}
var objOne = new obj(1,"objOneName");
var objTwo = new obj(2,"objTwoName");
alert("objOne名字为:"+objOne.getName());//提醒objOneName
delete objTwo.name;
alert("objOne名字为:"+objOne.getName());//提醒objOneName
in
:与for
一同运用用于遍历对象的属性名
在js中,for……in用于遍历一个对象的属性,把对象的属性名和属性值都提出来
for(var key in obj ){ alert(key); }
推断某个对象是不是具有某个属性
关于平常的对象属性需要用字符串指定属性的称号 如:var mycar = {make: "Honda", model: "Accord", year: 1998}; "make" in mycar // returns true "model" in mycar // returns true
关于数组对象,元素值对应的属性名为数字范例,如:
// Arrays var trees = new Array("redwood", "bay", "cedar", "oak", "maple"); 0 in trees // returns true 3 in trees // returns true 6 in trees // returns false "bay" in trees // returns false (you must specify the index number, // not the value at that index) "length" in trees // returns true (length is an Array property)
另外,假如你运用delete操作符删除了一个属性,再次用in搜检时,会返回false;
假如你把一个属性值设为undefined,然则没有运用delete操作符,运用in搜检,会返回true。
instanceof
: 推断范例
返回的是布尔值,而typeof
返回的是几种数据范例的字符串值
with
:援用一个对象,使接见属性与要领越发轻易
只能接见与修正属性,不能增添属性与要领
function obj(id,name){
this.id = id;
this.name = name;
this.getName = function(){
return this.name;
}
}
var myObj = new obj(3,"three");
with(myObj){
alert(id);//提醒3
alert(name);//提醒three
alert(getName());//提醒three
id = 4;
alert(id);//提醒4
}
alert(myObj.id);//提醒4,申明with中是经由过程援用体式格局接见的,而不是复制值的体式格局