/**
 * 防抖
 * @param {Function} func 执行的函数
 * @param {Number} wait 防抖的时间
 * @param {Boolean} immediate 是否为立即执行
 */
function debounce(func, wait, immediate) {
  let time = null;
  return function() {
    let _this = this;
    let args = arguments;
    if (time) clearTimeout(time);
    if (immediate) {
      let callNow = !time;
      setTimeout(() => {
        time = null;
      }, wait);
      if (callNow) func.apply(_this, args);
    } else {
      time = setTimeout(() => {
        func.apply(_this, args);
      }, wait);
    }
  };
}