手写节流防抖的实现

防抖

包括要不要点击后立即执行，还是要一段时间后执行

function debounce(func, wait, immediate) {
    
    
  let timeOut, result;
  let debounced = function () {
    
    
    //立即执行
    let context = this;
    let args = arguments;
    if (timeOut) clearTimeout(timeOut);
    if (immediate) {
    
    
      let callNow = !timeOut;
      timeOut = setTimeout(function () {
    
    
        timeOut = null;
      }, wait);
      if (callNow) result = func.apply(context, args);
    }
    //不会立即执行
    else {
    
    
      timeOut = setTimeout(function () {
    
    
        //绑定dom节点
        result = func.apply(context, args);
        timeOut = null;
      }, wait);
    }
    return result;
  };
  debounced.cancel = function () {
    
    
    clearTimeout(timeOut);
    timeout = null;
  };
  return debounced;
}

节流

//包括第一次会执行，最后一次也会执行
function throttle(func, wait, options) {
    
    
  let timeOut;
  let old = 0;
  if (!options) options = {
    
    };
  return function () {
    
    
    let context = this;
    let args = arguments;
    let now = new Date.valueOf();
    if (options.leading === false && !old) {
    
    
      old = now;
    }
    if (now - old > wait) {
    
    
      if (timeOut) {
    
    
        //第一次会直接执行
        clearTimeout(timeOut);
        timeOut = null;
      }
      func.apply(context, args);
      old = now;
    } else if (!timeOut && options.trailing !== false) {
    
    
      //最后一次也会被执行
      timeOut = setTimeout(function () {
    
    
        func.apply(context, args);
        timeOut = null;
      }, wait);
    }
  };
}