JS快速建立一個數組，長度100，值是下標或者0

1.Object.keys和Array.apply和map

var arr = Object.keys(Array.apply(null, { length: 100 })).map(function(
   item
) {
   return +item;
});

2.Object.keys和Array.from和map

 var arr = Object.keys(Array.from({ length: 100 })).map(function(item) {
    return +item;
  });

3.擴展運算符和Array.from

var arr=[...Array.from({ length: 100 }).keys()]

4.擴展運算符和Array.apply

var arr=[...Array.apply({ length: 100 }).keys()]

5.擴展運算符和new Array()

var arr = [...new Array(100).keys()];

6.擴展運算符和Array()

var arr = [...Array(100).keys()];

7.Array.from =>k

var arr = Array.from({ length: 100 }, (v, k) => k);
// 值爲0
 var arr = Array.from({ length: 100 }, ()=>0);

8.遞歸調用

var s = [];
var i =0;
function array(num){
   if(i<100){
    s[i] = i++
    array(num);
  }
  return s;
}
console.log(array(100));

值爲0

1.  var arr = new Array(100).fill(0);   
2.  var arr =  [...Array(100).fill(0)];
3.  var arr = new Array(101).join(0).split("").map(item => {
          return +item;
 });
 4. var arr = new Array(100);arr = arr.map(item=>0);
 5. Array.apply(null, { length: 100 }).fill(0);