this object in JS

Question

var str="hello";
var obj={
str:"world",
saysstr:this.str
};
alert(obj.saystr); / /The result is hello

May I ask why the result is "hello" instead of "world"

Answer 1

This article can solve most of this problems.

Answer 2

this指向什么，由包含它的最近的一个function决定的；
如果没找到function，那么this is the global object.
In your question, it’s the latter.

Modify the code slightly:

var str="hello";
var obj={
str:"world",
saystr: function() {
     alert(this.str)
}
};
obj.saystr();

This is the first situation.

To summarize: Determining this usually takes two steps:

1. First find the nearest this的最近的一个function containing

   ;

2. functionThen look at the way this

   is called. See here for details.

🎜

Answer 3

  alert(obj.saystr);
这句话实际等同于：

 alert(this.str);

Answer 4

Convert the question to the following for better understanding:

var str = "hello";
var obj = {};
obj.str = "world";
obj.saystr = this.str;

So you can see at a glance that this points to the window global object, so the result of obj.saystr is hello