gistfile1.js

// @author James Padolsey
// originally posted @ http://stackoverflow.com/questions/1837056

Array.prototype.binarySearch = function(v) {

    /* ARRAY MUST BE SORTED */

    if ( !this.length ) { return false; }
    if ( this[0] === v ) { return true; }

    var i, mid,
        start = 0,
        end = this.length,
        c = false;

    while ( c = (i = this[mid = start+((end-start)>>1)]) !== v ) {

        i < v ? (start = mid) : (end = mid);

        if (start >= end - 1) { break; }

    }

    return !c;

};