• forEach()
  • for in
  • for of

forEach 这边只能打印出来1234 desc不能打出来

var myArray = [1,2,3,4];
myArray.desc = " four number ";
myArray .forEach( value => console.log(value));

for in 这个打印出来的是数组的下标跟属性的名字,也可以打印出值跟属性的值

1.打印出数组的下标跟属性的名字
var myArray = [1,2,3,4];
myArray.desc = " four number ";
   for ( var n in myArray ) {
    console.log(n);
  }
2.打印出可以打印出值跟属性的值
var myArray = [1,2,3,4];
myArray.desc = " four number ";
   for ( var n in myArray ) {
    console.log(myArray[n]);
  }

for of 循环对象或者数组的值，可以break掉

var myArray = [1,2,3,4];
myArray.desc = " four number ";
   for ( var n of  myArray ) {
     if (n > 2)  break;
      console.log(n);
  }
这里的desc也没有打出来哦