JS 函数节流

  const throttle = function throttle(func, wait) {
        if (typeof func !== "function") throw new TypeError('func must be an function');
        if (typeof wait !== "number") wait = 300;
        let timer,
            previous = 0;
        return function proxy(...params) {
            let now = +new Date(),
                remaining = wait - (now - previous),
                self = this,
                result;
            if (remaining <= 0) {
                if (timer) {
                    clearTimeout(timer);
                    timer = null;
                }
                result = func.call(self, ...params);
                previous = now;
            } else if (!timer) {
                timer = setTimeout(() => {
                    if (timer) {
                        clearTimeout(timer);
                        timer = null;
                    }
                    result = func.call(self, ...params);
                    previous = +new Date();
                }, remaining);
            }
            return result;
        };
    };