Comparing and cloning objects in JavaScript

Here’s a handy way to determine if two JavaScript objects are identical without using a framework like jQuery or MooTools:


var compare_objects = function (obj1, obj2){

    var parameter_name;
    
    var compare = function(objA, objB, param){
        
        var param_objA = objA[param],
            param_objB = (typeof objB[param] === "undefined") ? false : objB[param];
        
        switch(typeof objA[param]){
            case "object": return (compare_objects(param_objA, param_objB));
            case "function": return (param_objA.toString() === param_objB.toString());
            default: return (param_objA === param_objB);
        }
        
    };
    
    for(parameter_name in obj1){
        if(typeof obj2[parameter_name] === "undefined" || !compare(obj1, obj2, parameter_name)){
            return false;
        }
    }

    for(parameter_name in obj2){
        if(typeof obj1[parameter_name] === "undefined" || !compare(obj1, obj2, parameter_name)){
            return false;
        }        
    }

    return true;

};

Here’s an easy way to clone a JavaScript object:


var clone_object = function (original_obj) {
    var new_obj = {};
    for(var param in original_obj) {
        if(original_obj.hasOwnProperty(param)){
            if(typeof(original_obj[param]) === "object"){
                new_obj[param] = clone_object(original_obj[param]);
            } else {
                new_obj[param] = original_obj[param];
            }
        }
    }
    return new_obj;
};

A real-world example of the two functions:


var object_1 = { fruit: "apple", tree: "dogwood", number: 3 };
var object_2 = { fruit: "apple", tree: "dogwood", number: 3, cartoons: { anime: "robotech", fantasy: "he-man" } };
var object_3 = clone_object(object_2);

console.log("objects 1 and 2 match? " +compare_objects(object_1, object_2));
//displays false;

console.log("objects 2 and 3 match? " +compare_objects(object_2, object_3));
//displays true

Bear in mind both of these functions are recursive, which means the larger the object, the slower the performance.

New SCORM ebook coming soon!

I'm writing an ebook explaining how to build an HTML-based SCORM course. Subscribe to be notified when it's ready, as well as receive early bird pricing and some free goodies!

No spam, no sharing your email address, unsubscribe at any time. Powered by ConvertKit
Advertisements