On call and apply methods in JS

clipboard.png

questions you want to answer:

  • Why can"t the call method be called through apply ?
  • Why is the second and third output -Infinity ?
  • Why does the Reflect object provide only the apply method and not the call method?

I don"t know if my understanding is wrong. In short, this question has been bothering me for a long time. I hope a great god can help me solve it.

Javascript
May.09,2022
The usage of

is wrong in itself. The first parameter of call and apply is the this passed to it when the target function is called. You use this to pass the function to this to call or apply , so it's wrong, but just happens to support this calling method in the first way.

you need to figure out the function and difference between call () and apply () , both of which change the direction of the this object. For example: 

var obj = {
   name:"abcd"
}
function fn1(){
    console.log(this.name);//undefined
}
function fn2(){
   fn1.call(obj,null);
   console.log(this.name);//abcd
}

replacing call with apply has the same result. The difference between the two is that the passed parameter, the first parameter is the object to be changed, the second parameter is different, call passes an array item parameter, apply passes an array parameter, or it can be the function's arguments object. For example, 

var obj2 = {
    name:'abcd',
    sex:'xx'
}

function fn1(name,sex){
  return name + sex;
}
function fn2(){
   return fn1.apply(obj2,['hhh','male']);//hhhmale
}

both methods are non-inherited.

thanks for inviting ~ you can read these two articles, and then look back at your own questions, which should answer your questions.
JS Magic Hall: get to know Function.prototype.call
interviewer asked: can you simulate the call and apply methods of JS

Previous: The vue component page, which uses axios to request data asynchronously, returns an unassigned data. The reading bar on the page is refreshed, similar to the effect of page switching.

Next: Iview Select component reported an error ~

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-42b5c12-6769.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-42b5c12-6769.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?