第九篇 手写原理代码 - 数组 【 实现 forEach、map、filter、every、some 】

1、forEach

Array.prototype.my_forEach = function (callback) {
  for (let i = 0; i < this.length; i++) {
    callback(this[i], i, this);
  }
};

2、map

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

3、filter

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

4、every

Array.prototype.my_every = function (callback) {
  let flag = true;
  for (let i = 0; i < this.length; i++) {
    flag = callback(this[i], i, this);
    if (!flag) break;
  }
  return flag;
};

5、some

Array.prototype.my_some = function (callback) {
  let flag = false;
  for (let i = 0; i < this.length; i++) {
    if (callback(this[i], i, this)) {
      flag = true;
      break;
    }
  }
  return flag;
};

使用

const arrTest = [
  { name: "caix-1987", age: 24 },
  { name: "caix-1988", age: 23 },
  { name: "caix-1989", age: 22 },
];

arrTest.my_forEach((item, index, arr) => {
  console.log("my_forEach", item, index, arr);
});

const my_map_data = arrTest.my_map((item) => {
  return item.age;
});

const my_filter_data = arrTest.my_filter((item) => {
  return item.age > 23;
});

const my_every_data = arrTest.my_every((item) => {
  return item.age > 23;
});

const my_some_data = arrTest.my_some((item) => {
  return item.age > 23;
});