JavaScript uses Object.keys to traverse object property names

In the actual development, we sometimes need to know all the attributes of the object, JS native gives us a good method: Object.keys, the method returns an array

var obj = {

' a ': ' 123 ',

' B ': ' 345 ',

};

Console.log (Object.keys (obj)); [' A ', ' B ']

It is noteworthy that if a string is passed in the keys method, the array is returned, except that the value in the array is the index of each character in the string:

var str = ' ab1234 ';

Console.log (Object.keys (obj)); [0,1,2,3,4,5]

example, traversing an array and traversing the object's differences

<script>     //----------------for traversing array objects-    var i,myarr
 = [1,2,3];     for  (var i = 0; i < myarr.length; i++)
 {        console.log (i+ ":" +myarr[i));
    };     //---------for-in  is used to traverse the     var man ={hands:2 of a non-array object.
LEGS:2,HEADS:1};     //adds a clone method to all objects, adding prototype properties to the built-in prototypes (Object,array,function), which is powerful and dangerous      if (typeof object.prototype.clone === "undefined") {         object.prototype.clone = function () {};         }      //    for (var i in man) {         if  (Man.hasownproperty (i))  { //filter, output only the private properties of man              console.log (i, ":", Man[i]);
        }; &NBSP;&NBSP;&NBSP;&NBSP}     //output to Print hands:2,legs:2,heads:1      for (Var i in man)  {//does not use filtration         
Console.log (i, ":", Man[i]);     }         //Output is     // Hands : 2 index.html:20     //legs : 2 index.html:20      //heads : 1 index.html:20     //clone : function   () {}      for (Var i in man)  {         if (Object.prototype.hasOwnProperty.call (man,i))  { //filtration              console.log (i, ":", Man[i]); &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP}    &nbsp}    //output is print  Hands:2,legs:2,heads:1 </script>