兼容低版本includes不支持问题

//可以放在main.js上，然后再需要用的地方直接调用

if (!Array.prototype.includes) {
  Object.defineProperty(Array.prototype, 'includes', {
    value: function(valueToFind, fromIndex) {
      if (this == null) {
        throw new TypeError('"this" is null or not defined');
      }
      var o = Object(this);
      var len = o.length >>> 0;
      if (len === 0) {
        return false;
      }
      var n = fromIndex | 0;
      var k = Math.max(n >= 0 ? n : len - Math.abs(n), 0);
      function sameValueZero(x, y) {
        return x === y || (typeof x === 'number' && typeof y === 'number' && isNaN(x) && isNaN(y));
      }
      while (k < len) {
        if (sameValueZero(o[k], valueToFind)) {
          return true;
        }
        k++;
      }
      return false;
    }
  });
}