The "This" parameter in JavaScript

When a function is called, there is an implicit parameter----the This----is also assigned, in addition to the parameters that are explicitly declared when the function definition is assigned.

This parameter points to an object that is implicitly related to the function call, which is referred to as the context of the function (functions context), or called the invocation context (invocation contexts), and may feel clearer.

When called as a function

Function Ninja () {};

Ninja ();

In this case, the function context is the global context----the Window object.

When called as a function, the function is defined in the Window object, but in principle it is the same as the function being called as a method call.

When called as a method

var o = {};

O.whatever = function () {};

O.whatever ();

Points to the owning object.

Called as a constructor

When the constructor is called, the following behavior occurs:

A new empty object is created

The object is passed as a parameter to the constructor and becomes the function context of the constructor function

The new object is returned as the return value of the constructor function

Through the Apply () and call () methods

Juggle.apply (NINJA1, [1,2,3,4]);

Juggle.call (NINJA2, 5,6,7,8);

The context in which a function call can be explicitly defined

　　

References: <secrets of the JavaScript ninja>

The "This" parameter in JavaScript