// 使用场景：防止狂点
function debounce(fn,delay=500){
	// 使用vue的话, debounce.timer 换成 this.timer 
	debounce.timer && clearTimeout(debounce.timer) ;
	debounce.timer = setTimeout(()=>{
	// fn....
		debounce.timer = null
	},delay)
}

throttle (func, delay) {     
    let timer = null;     
    let startTime = Date.now();     
    return function() {             
        const curTime = Date.now();             
        const remaining = delay - (curTime - startTime); 
        timer && clearTimeout(timer);  
  //使用场景 window.addEventListener('scroll', throttle(fn, 1000));
  
  //添加事件一段时间不滚动，remaining < 0保证了第一次触发事件就能立即执行事件处理函数
        if (remaining <= 0) {                 
            func.apply(this, arguments);                    
            startTime = Date.now();              
        } else {                    
            timer = setTimeout(func, remaining);              
        }      
    }
}