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js如何实现原生map

js原生方法map实现,代码如下:

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <meta name="author" content="杨欣">
  <title>map</title>
</head>

<body>

  <script>
    Array.prototype.my_map = function (callback) {
      if (!Array.isArray(this) || !this.length || typeof callback !== 'function') {
        return []
      } else {
        let result = [];
        for (let index = 0; index < this.length; index++) {
          const element = this[index];
          result.push(callback(element, index, this))
        }
        return result
      }
    }

    let arr = [1, 2, 3, 4, 5]
    let res = arr.my_map((ele, i) => {
      return ele + 10
    })
    console.log(res)
  </script>
</body>

</html>

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