The four ways to call the JS function and the corresponding this point

A function call, at which point this is the global window

1 var c=function () {2    alert (this = =window)3  }  4   C ()//true

Second, method invocation

var myobj={  value:2,  inc:function (num) {   alert (this. value+num);  } } myobject.inc (1// result 3, because this points to myobj

Note: The internal anonymous function does not belong to the current object's function, so this refers to the Global object window

varmyobj={name:'MyObject', Value:0, increment:function (num) { This. Value + =typeof(num) = = =' Number'? Num:0; }, Tostring:function () {return '[object:'+ This. name+'{value:'+ This. value+'}]'; }, Getinfo:function () {return(function () {return  This. toString ();//The internal anonymous function does not belong to the current object's function, so this is a pointer to the Global object window      })(); }}alert (Myobj.getinfo ());//[Object window];

Workaround:

 varmyobj={name:'MyObject', Value:0, increment:function (num) { This. Value + =typeof(num) = = =' Number'? Num:0; }, Tostring:function () {return '[object:'+ This. name+'{value:'+ This. value+'}]'; }, Getinfo:function () {varthis= This;//Save the current this point first .   return(function () {returnthis.tostring ();  })(); }}alert (Myobj.getinfo ());//[Object:myobject {value:0}]

Third, use the new keyword to create a new function object call, this point is bound to the instance of the constructor

var fn = function (status) {  this. Status== function () {     return thisvarnew fn ('my status'  ); alert (test.get_status); // my status,this points to test

Four, Apply/call call

function MyObject (name) { This. name=name | |'MyObject';  This. value=0;  This. increment=function (num) { This. Value + =typeof(num) = = =' Number'? Num:0;  };  This. tostring=function () {return '[Object:'+ This. name+'{value:'+ This. value+'}]';   };  This. target= This; } function GetInfo () {return  This. toString ();} varmyobj=NewMyObject (); Alert (getinfo.apply (MYOBJ));//[Object:myobject {value:0}],this points to myobjAlert (getinfo.apply (window));//[Object Window],this point to Window

Using call and apply, you can redefine the execution environment of the function, which is the point of this, which is very common for some applications.

The four ways to call the JS function and the corresponding this point