Array.prototype.filter

[Sunny]

Array.prototype.myFilter = function (callback) {
  const res = [];
  for (let i = 0; i < this.length; i++) {
    callback(this[i], i, this) && res.push(this[i]);
  }
  return res;
};

[hannah]

Array.prototype.filter = function(callback, thisArg) {
  if (this == undefined) {
    throw new TypeError('this is null or not undefined');
  }
  if (typeof callback !== 'function') {
    throw new TypeError(callback + 'is not a function');
  }
  const res = [];
  // 让O成为回调函数的对象传递（强制转换对象）
  const O = Object(this);
  // >>>0 保证len为number，且为正整数
  const len = O.length >>> 0;
  for (let i = 0; i < len; i++) {
    // 检查i是否在O的属性（会检查原型链）
    if (i in O) {
      // 回调函数调用传参
      if (callback.call(thisArg, O[i], i, O)) {
        res.push(O[i]);
      }
    }
  }
  return res;
}

[beary]

Array.prototype.filter = function (callback) {
  const res = [];
  for (let i = 0; i < this.length; i++) {
    callback(this[i], i, this) && res.push(this[i]);
  }
  return res;
};

[kangkang123269]

Array.prototype.filter = function(callback, thisArg) {
  var result = [];
  for (var i = 0; i < this.length; i++) {
    if (callback.call(thisArg, this[i], i, this)) {
      result.push(this[i]);
    }
  }
  return result;
}