浅拷贝扩展

extend.js

function extend() {
    var target = arguments[0] || {};
    var arrs = slice.call(arguments, 1);
    var len = arrs.length;

    for (var i = 0; i < len; i++) {
        var arr = arrs[i];
        for (var name in arr) {
            target[name] = arr[name];
        }

    }
    return target;
}