js原生方法map实现

<!DOCTYPE html>

<html lang="en">

<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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js原生方法map实现

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