<!DOCTYPE HTML><HTMLLang= "en"><Head> <MetaCharSet= "UTF-8"> <title>Title</title></Head><Body></Body><Script> vara={User:"chasing the dream son", fn:function() {Console.log ( This. User); } }; varb=A.fn; b (); //undefined//for what? Because JS in the direction of this, always look at the time of execution is who call him, but when the A.fn copy to B is not called, is in the window Global environment, the final point is window. //Call apply bind is to change the point of this problem in JS//1 Call vara={User:"chasing the dream son", fn:function() {Console.log ( This. user);//chasing the dream son } }; varb=A.fn; B.call (a);//by using the call method, add B to the environment of a, in fact, let this continue to point to a environment. //The call method can add multiple parameters in addition to the first argument, as follows vara={User:"chasing the dream son", fn:function(E,ee) {Console.log ( This. User); //chasing the dream sonConsole.log (E+ee); //3 } } varb=A.fn; B.call (A,1,2);//2 Apply vara={User:"chasing the dream son", fn:function() {Console.log ( This. user);//chasing the dream son } }; varb=A.fn; B.apply (a);//with the same effect as call, add B to an environment, change this point to//Unlike call, apply can also specify parameters, but the parameters are in the form of an array//var a = {//User: "Chasing the Dream Son",//fn:function (e,ee) {//Console.log (This.user);//Chase Dream son//Console.log (e+ee);//11// }// }//var b = A.fn;//b.apply (a,[10,1]);// *********************//Note If the first argument to call and apply is NULL, then this refers to the Window object//3 Bind vara={User:"chasing the dream son", fn:function() {Console.log ( This. User); } }; varb=A.fn; B.bind (a);//bind can also change the point of this, we find that the code is not printed, yes,//This is the difference between bind and call, the Apply method, in fact the Bind method returns a modified function. //You also need to perform this function manually varC=B.bind (a); C ()//OK, the same bind can have multiple parameters, and the parameters can be executed again when added, but note that the parameters are in the order of the formal parameter vara={User:"chasing the dream son", fn:function(e,d,f) {Console.log ( This. User); //chasing the dream sonConsole.log (e,d,f);//Ten 1 2 } } varb=A.fn; varC=B.bind (A,Ten); C (1,2);// ******************//Summary: Call and apply are all changes in the context of this and immediately execute this function,//The Bind method allows the corresponding function to think about when the call is made, and can add parameters to the execution.//This is the difference between them, according to their actual situation to choose to use. </Script></HTML>
JS in the call apply Bind
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