js对象深潜拷贝（从requirejs中抠出来的）

var op = Object.prototype,
    ostring = op.toString,
    hasOwn = op.hasOwnProperty;

function isFunction(it) {
    return ostring.call(it) === '[object Function]';
};

function isArray(it) {
    return ostring.call(it) === '[object Array]';
};
function hasProp(obj, prop) {
    return hasOwn.call(obj, prop);
};
function eachProp(obj, func) {
    var prop;
    for (prop in obj) {
        if (hasProp(obj, prop)) {
            if (func(obj[prop], prop)) {
                break;
            }
        }
    }
};
/**
 * Simple function to mix in properties from source into target,
 * but only if target does not already have a property of the same name.
 *
 * @param {target} 目标对象
 * @param {source} 源对象
 * @param {force} 是否强制覆盖目标对象已有的属性
 * @param {deepStringMixin} 是否深拷贝递归操作
 *
 * @returns {target}
 */
function mixin(target, source, force, deepStringMixin) {
    if (source) {
        eachProp(source, function (value, prop) {
            if (force || !hasProp(target, prop)) {
                if (deepStringMixin && typeof value === 'object' && value &&
                    !isArray(value) && !isFunction(value) &&
                    !(value instanceof RegExp)) {

                    if (!target[prop]) {
                        target[prop] = {};
                    }
                    mixin(target[prop], value, force, deepStringMixin);
                } else {
                    target[prop] = value;
                }
            }
        });
    }
    return target;
};


调用：
var obj = {
    name:'Tom',
    age:19,
    children:{
        name:'Jack',
        age:30
    }
};
var obj2 = mixin({},obj,false,true);
obj.children.name='Marry';
console.log(obj2);