Javascript Array existsByKey(key, val)

/*/*from   ww  w  .jav a 2s  . com*/
 * Utility Extension to look into an array
 * of objects by key to determine if it exists already
 */

Array.prototype.existsByKey = function(key, val) {
 var exists = this.map(function(obj) { return obj[key] }).indexOf(val) != -1;
 console.log('Does \'' + val + '\' exist? ' + exists);
 return exists;
}