I’ve been work­ing on a selector engine recently, and given the com­plex­ity of it, it’s easier to return a multi-dimensional array than a flat one (for example: [['this'], 'is', ['an', 'example']] instead of ['this', 'is', 'an', 'example']). Of course, return­ing such an array to another func­tion is a bit point­less because it requires that func­tion to tra­verse through the array in order to flat­ten it so it can be used effi­ciently. Another prob­lem with the selector engine is that some­times, an ele­ment can be returned twice (for example: $('div, #content'), where #content is a div). Because of this, I wrote a tidy func­tion that flat­tens the array and removes duplic­ate indexes.

Unfor­tu­nately, it requires some addi­tional code:

indexOf

Returns the first index where a value (searchStr) appears. startIndex allows you to begin the search at a pre­defined index.

Array.prototype.indexOf = Array.prototype.indexOf || function(searchStr, startIndex) {
	for(var i = startIndex || 0, thisLength = this.length; i < thisLength; i++) {
		if(searchStr === this[i]) {
			return i;
		}
	}

	return -1;
};

inArray

Returns either true or false if a value (searchStr) is in an array. startIndex allows you to begin the search at a pre­defined index.

Array.prototype.inArray = function(searchStr, startIndex) {
	return this.indexOf(searchStr, startIndex) > -1;
};

flatten

Flat­tens a multi-dimensional array to a one-dimensional array.

Array.prototype.flatten = function() {
	for(var i = 0, thisLength = this.length, b = []; i < thisLength; i++) {
		if(this[i].constructor === Array) {
			this[i] = this[i].flatten();

			for(var j = 0, thisILength = this[i].length; j < thisILength; j++) {
				b.push(this[i][j].constructor === Array ? this[i][j].flatten() : this[i][j]);
			}
		}
		else {
			b.push(this[i]);
		}
	}

	return b;
};

tidy

Tidies up an array by remov­ing dupe val­ues and flat­ten­ing it to a one dimen­sional array.

Array.prototype.tidy = function() {
	var a = this.flatten();
	var b = [];

	for(var i = 0, aLength = a.length; i < aLength; i++) {
		if(!b.inArray(a[i])) {
			b.push(a[i]);
		}
	}

	return b;
};

All this code has been tested on the fol­low­ing browsers and works perfectly:

• Fire­fox 1.5, 2, 3, 3.5
• Chrome 1, 2, 3
• Opera 7, 8, 9.5, 9.64, 10
• Safari 3, 4
• Inter­net Explorer 6, 7, 8