function subTimeStr(str) {
  if (!str || typeof str != "string") return;
  let index = str.indexOf(" ");
  return str.substring(0, index);
}

function datetimeFormat(type = "yyyy-MM-dd HH:mm:ss", t = new Date()) {
  let timer, W;
  let _d = new Date(t);
  let yyyy = _d.getFullYear();

  let M,
    MM = _d.getMonth() + 1;
  if (MM < 10) MM = "0" + MM;

  let d,
    dd = _d.getDate();
  if (dd < 10) dd = "0" + dd;

  let h,
    hh,
    H,
    HH = _d.getHours();
  if (h > 12) h = h - 12;
  if (hh > 12) hh = hh - 12;
  if (hh < 10) hh = "0" + hh;
  if (HH < 10) HH = "0" + HH;

  let mm = _d.getMinutes();
  if (mm < 10) mm = "0" + mm;

  let ss = _d.getSeconds();
  if (ss < 10) ss = "0" + ss;

  let w = _d.getDay();
  if (0 == w) w = 7;

  switch (type) {
    case "yyyy-MM-dd HH:mm:ss": {
      timer = `${yyyy}-${MM}-${dd} ${HH}:${mm}:${ss}`;
      break;
    }

    case "MM-dd HH:mm:ss": {
      timer = `${MM}-${dd} ${HH}:${mm}:${ss}`;
      break;
    }

    case "yyyy-MM-dd": {
      timer = `${yyyy}-${MM}-${dd}`;
      break;
    }

    case "HH:mm:ss": {
      timer = `${HH}:${mm}:${ss}`;
      break;
    }

    case "yyyy/MM/dd": {
      timer = `${yyyy}/${MM}/${dd}`;
      break;
    }

    case "年月日": {
      timer = `${yyyy}年${M}月${d}日`;
      break;
    }

    case "年月月日日": {
      timer = `${yyyy}年${MM}月${dd}日`;
      break;
    }
  }
  return timer;
}

const throttle = (fn, wait) => { //节流
  var prev = Date.now();
  return function () {
    var context = this;
    var args = arguments;
    var now = Date.now();
    console.log(now - prev > wait)
    if (now - prev > wait) {
      fn.apply(context, args)
      prev = Date.now()
    }
  }
}
const debounce = (func, wait) => { //防抖
  // wait：500ms；func：被频繁触发的事件
  let timeout;
  return function () {
    let context = this;
    let args = arguments;
    let later = () => {
      timeout = null;
      func.apply(context, args);
    };
    clearTimeout(timeout);
    timeout = setTimeout(later, wait);
  }
}

module.exports = {
  subTimeStr,
  datetimeFormat,
  throttle,
  debounce
}