compare a string to given param to see if its similar

String.prototype.similarTo.js

/*	String.prototype.similarTo	*/
(function() {	//	compare a string to given param to see if its similar
	//	pass 2nd param true to have it check in reverse as well
    function a(a, c) {
        if (0 == a.length) return c.length;
        if (0 == c.length) return a.length;
        for (var d = [], e = 0; e <= c.length; e++) d[e] = [e];
        for (var f = 0; f <= a.length; f++) d[0][f] = f;
        for (e = 1; e <= c.length; e++)
            for (f = 1; f <= a.length; f++) c.charAt(e - 1) == a.charAt(f - 1) ? d[e][f] = d[e - 1][f - 1] : d[e][f] = Math.min(d[e - 1][f - 1] + 1, Math.min(d[e][f - 1] + 1, d[e - 1][f] + 1));
        return d[c.length][a.length]
    }

    function g(b, c) {
        var d = this.toString(),
            e = a(d, b);
        if (!c) var f = b.reverse(),
            d = a(d, f),
            e = e < d ? e : d;
        return e;
    }
	
    Object.defineProperty && !String.prototype.hasOwnProperty("similarTo") &&
        Object.defineProperty(String.prototype, "similarTo", {
            value: g
        })
})();