The understanding of this in js

Preface:This object will only work when strict mode is not used. The this object is bound by the execution environment of the function at runtime.

Case 1: In the global function, this is equal to window. Only when the function is called as a method of an object, this will be equal to that object. If you still don’t know what a global function is, please refer here and click to open the link

Case 2: The execution environment of the anonymous function is global, this usually points to the window

For example

var name = "window"; var object = { name: "Object name", getNameFunc: function () { return function (){ return this.name; }; } }; console.log(object.getNameFunc() ()); // 输出window

Case 3: Save the this object in the external scope in a variable that can be accessed by the closure, so that this can point to the this object in the scope

For example

var name = "window"; var object = { name: "Object name", getNameFunc: function () { var that = this; return function (){ return that.name; }; } }; console.log(object.getNameFunc() ()); // 输出Object name

Case 4: Assign the function first and then execute it, the value of this cannot be maintained

For example

var name = "window"; var object = { name: "Object name", getName: function () { return this.name; } }; console.log((object.getName = object.getName) ()); // 输出window

Case 5: If the execution environment of the function is changed through call or apply, thiswill point to other objects

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