手动实现 forEach 函数

废话不多说，直接上代码！

Array.prototype.forEach = 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;
  while (i < length) {
    callback(this[i], i, this);
    i++;
  }
};