Jsの练习-数组其他常用方法 -map() ，filter() ，every() ，some()

map() ：映射，对数组中的每一项运行给定函数，返回每次函数调用结果组成的函数。

<!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">
    <title>Document</title>
</head>

<body>
    <script>
        var arr = [, , , , , ];
        var newArr = arr.map(function (value, index) {
            return value * value;
        })

        console.log(newArr);
    </script>

</body>

</html>

map()

filter():过滤，对数组中的每一项运行给定函数，返回满足过滤条件组成的数组。

filter()

<!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">
    <title>Document</title>
</head>

<body>
    <script>
        var arr = [, , , , , , , , , , ];
        var newArr = arr.filter(function (value, index) {
            return index %  ===  || value >= ;
        });
        console.log(newArr);
    </script>

</body>

</html>

every(): 判断数组中每一项是否满足条件，只有所有项都满足条件，才会返回true。

every()

<!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">
    <title>Document</title>
</head>

<body>
    <script>
        var arr = [, , , , ];

        var newArr = arr.every(function (value, index) {
            return value < ;
        })

        console.log(newArr);
    </script>

</body>

</html>

some():判断数组中是否存在满足条件的项，只要有一项满足条件，就会返回true。