节流函数

释意：不管接口请求了多少次，调用节流我只请求一次

fnThrottle (method, delay) {

    var timer = this.timer;

    return _=>{

        var context = this;

        var args = arguments;

        clearTimeout(timer);

        this.timer=setTimeout(_=>{

            method.apply(context,args);

        },delay);

    }

},