Is there a better way to copy an array onto the this variable
function obj(arr) {
for (var i=0, l=arr.length; i<l; ++i) {
this[i] = arr[i];
}
this.length = arr.length;
}
var o = new obj([1,2,3,4]);
console.log(o[0]); // Outputs 1
Is there any other way to do it, instead of iterating over the whole arr ?
You can use Array#push this way:
function obj(arr) {
Array.prototype.push.apply(this, arr);
}
This will treat this like an array, adding all the elements from arr and setting length correctly. See also Function#apply.
But of course there is still an internal loop. You cannot copy / move a collection values to another collection without iterating over it (unless, I guess, the collections use structural sharing)
You could do it like this:
function obj() {
return this;
}
var o = obj.apply([1,2,3,4]);
console.log(o[0]); // Outputs 1
