I have this strange problem when I shuffle an array in javascript and I have no clue what's the problem. Can somebody help me?
When I shuffle an array like this
[1,2,3,4,5,6,7,8,9,10]
I get a null value, like this
[null,10,1,8,9,3,2,7,6,4]
This is the code (http://jsfiddle.net/2m5q3d2j/):
Array.prototype.suffle = function () {
for (var i in this) {
var j = Math.floor(Math.random() * this.length);
this[i] = this[j] + (this[j] = this[i], 0);
}
return this;
};
Because you're adding an enumerable property (shuffle) to Array.prototype, if you insist on iterating with for-in, you need to add a hasOwnProperty test:
Array.prototype.shuffle = function () {
for (var i in this) {
if ( this.hasOwnProperty(i) ) {
var j = Math.floor(Math.random() * this.length);
this[i] = this[j] + (this[j] = this[i], 0);
}
}
return this;
};
Otherwise I would rather suggest:
Array.prototype.shuffle = function () {
for (var i=0; i < this.length; i++) {
var j = Math.floor(Math.random() * this.length);
this[i] = this[j] + (this[j] = this[i], 0);
}
return this;
}
http://jsfiddle.net/2m5q3d2j/5/
You can also use Object.defineProperty to create the property, to avoid making it enumerable, on ES5+ engines.
for-in to loop through arrays, there are better ways that don't have this problem.
for (var i = 0; i < this.length; i++) is better?
for-into loop through arrays (without safeguards, and there are better ways). More: stackoverflow.com/questions/9329446/…