index.js

module.exports = function (obj) {
    if (!obj || typeof obj !== 'object') return obj;
    
    var copy;
    
    if (isArray(obj)) {
        var len = obj.length;
        copy = Array(len);
        for (var i = 0; i < len; i++) {
            copy[i] = obj[i];
        }
    }
    else {
        var keys = objectKeys(obj);
        copy = {};
        
        for (var i = 0, l = keys.length; i < l; i++) {
            var key = keys[i];
            copy[key] = obj[key];
        }
    }
    return copy;
};

var objectKeys = Object.keys || function (obj) {
    var keys = [];
    for (var key in obj) {
        if ({}.hasOwnProperty.call(obj, key)) keys.push(key);
    }
    return keys;
};

var isArray = Array.isArray || function (xs) {
    return {}.toString.call(xs) === '[object Array]';
};