Roll your own 'each' function

each.js

function each(obj,callback){
    // Ensure callback is a function
    if (!callback || typeof(callback) !== "function") {
        throw new Error("Callback is not a function.");
        return false;
    }
    
    // If obj is an array
    if(obj.constructor === Array){
        for (var i=0, z=obj.length; i<z; i++){
            callback(i,obj[i]);
        }
    // If obj is an object
    }else{
        for (var i in obj){
            callback(i,obj[i]);
        }
    }
}