var arr = new Array(100);
for(var i=0;i<arr1.length;i++){
  arr1[i] = i;
}

var arr = new Array();
for(var i=0;i<100;i++){
  arr.push(i);
}

var arr = new Array();
var i = 0;
while(i<100){
  arr.push(i);
  i++;
}

var arr = new Array();
var i = 0;
do{
  arr.push(i);
  i++;
}
while(i<100)

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

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

var arr = Array.from(Array(100), (v,k) =>k);

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

var arr = [];
var i = 0;
var timer = setInterval(function(){
  arr[i] = ++i;
  if(i>=100){
    clearInterval(timer);
  }
},1);

var arr = [];
var i = 0;
function MakeArray(num){
  if(i<num){
    arr[i] = i++;
    MakeArray(num);
  }
  return arr;
}

var arr = new Array(100).toString().split(',').map(function(item,index){
  return index;
});