手动实现 map 函数

废话不多说，直接上代码！

Array.prototype.map = function (callback, thisArg) {
  if (this == null) {
    throw new TypeError("this is null or not defined");
  }
  if (typeof callback !== "function") {
    throw new TypeError(callback + " is not a function");
  }
  const length = this.length;
  let i = 0;
  let result = [];

  while (i < length) {
    result[i] = callback.call(thisArg, this[i], i, this);
    i++;
  }
  return result;
};

Array.prototype.map = function (callback, thisArg) {
  if (this == null) {
    throw new TypeError("this is null or not defined");
  }
  if (typeof callback !== "function") {
    throw new TypeError(callback + " is not a function");
  }

  return this.reduce((acc, cur, index, array) => {
    const res = callback.call(thisArg, cur, index, array);
    acc.push(res);
    return acc;
  }, []);
};