underscore无new构造

学习underscore.js有感

(function () {
    var root = this;
    var _ = function(obj) {
        if (obj instanceof _) return obj;
        if (!(this instanceof _)) return new _(obj);
        this._wrapped = obj;
    };
    if (typeof exports !== 'undefined') {
        if (typeof module !== 'undefined' && module.exports) {
            exports = module.exports = _;
        }
        exports._ = _;
    } else {
        root._ = _;
    }
    _.fun = function (str) {
        console.log(str)
    }
    _.prototype.fun = _.fun

}.call(this))
_.fun('fff')
var a = new _()
_.fun('aa')