Call of built-in object prototype

The publisher statement in publish/subscribe mode converts arguments to an array.

VaR ARGs = array. Prototype. Slice. Call (arguments, 0 );

This kind of built-in object prototype call can be used;

 

The "internal object prototype cannot be modified" as required in the encoding specification is similar to the following:

String.prototype.startsWith = function(text) {            return this.indexOf(text) == 0;        }

 

Arguments is an object.. It has [0], [1], length, which cannot represent an array, and it has other things.

Array arguments

 

function fn() {        console.log(typeof arguments);   //object        console.log(arguments instanceof Array); //false        for(var i = 0; i < arguments.length;i++) {            console.log(arguments[i]);        }        var arr = [1,2,3];        console.log(arr);    }

 

There isForeachUsage

function showResults(value, index) {        console.log(‘value:‘ + value);        console.log(‘index:‘ + index);    }
var arr = [‘nihao‘, ‘nibuhao‘, ‘nihaobuhao‘];
arr.forEach(showResults);

//console.log

Value: nihao
Index: 0
Value: nibuhao
Index: 1
Value: nihaobuhao
Index: 2

 

Arguments cannot use foreach

     function fn() {        arguments.forEach(showResults);    }    function showResults(value, index) {        console.log(‘value:‘ + value);        console.log(‘index:‘ + index);    }    fn(‘nihao‘, ‘nibuhao‘);    //Uncaught TypeError: undefined is not a function 

 

Call of built-in object prototype