SOURCE

 function debounce(func, wait, immediate) {
        let timer;
 
        return function () {
            //this指向debounce
            let context = this;
            //即参数，func,wait
            let args = arguments;
 
            //如果timer不为null, 清除定时器
            if (timer) clearTimeout(timer);
 
            //如果是立即执行
            if (immediate) {
                //定义callNow = !timer
                var callNow = !timer;
                //定义wait时间后把timer变为null
                //即在wait时间之后事件才会有效
                timer = setTimeout(() => {
                    timer = null;
                }, wait)
                //如果callNow为true,即原本timer为null
                //那么执行func函数
                if (callNow) func.apply(context, args)
            } else {
                //如果是不立即执行
                //那就是每次重新定时
                timer = setTimeout(function () {
                    func.apply(context, args)
                }, wait);
            }
        }
 }

const fn = () => {
    console.log('Click Me');
}

document.querySelector('#test').addEventListener('click', debounce(fn, 1000, true))

<button id="test">Click Me</button>