Merge/Extend Objects in native JS

mergeObjects.js

/*!
 * Replace some functionality of jQuery's $.extend() method
 * with only native JavaScript. Unlike $.extend(), this
 * function will ONLY merge plain objects (not arrays).
 * https://gist.github.com/Error601/9a181a0b9f414b752c38
 */

function mergeObjects( /* [true ,] obj1, obj2 [, ...] */ ){

    var args = arguments,
        arg1 = args[0],
        arg2 = args[1] || {},
        len  = args.length,
        deep = false,
        i, arg, output = {};

    function isObject( obj ){
        return Object.prototype.toString.call(obj) === '[object Object]';
    }

    // first argument will be output object
    if ( isObject(arg1) ){
        output = arg1;
    }
    // unless set to true
    else if ( arg1.toString() === "true" ){
        deep = true;
        output = arg2;
    }

    // stop here and return the output object
    // if argument length is 0 or 1, or
    // if we're trying to deep merge a single object
    if ( len <= 1 || (deep && len === 2) ){
        return output;
    }

    function processObject( obj ){
        var prop;
        for ( prop in obj ){
            if ( obj.hasOwnProperty(prop) ){
                if ( deep && isObject(obj[prop]) ){
                    output[prop] = mergeObjects( deep, output[prop], obj[prop] );
                }
                else {
                    output[prop] = obj[prop];
                }
            }
        }
    }

    // loop over additional arguments
    for ( i = 1; i < len; i++ ){
        arg = args[i];
        if ( isObject(arg) ) {
            processObject(arg);
        }
    }

    return output;

}

Of course there are plenty of libraries with methods to do exactly what this code snippet does, but... If you need to merge some objects before those load (or are just too "hardcore" to use external libraries), now there's this. So there ya go.