arr.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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let arr2 = arr.filter(item => {
if (item % 2 == 0) {
return false;
} else {
return true;
}
})
console.log(arr);
console.log(arr2);
</script>
</head>
<body>
</body>
</html>
arr.filter2
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let arr2 = arr.filter(item => item % 2 == 0);
console.log(arr);
console.log(arr2);
</script>
</head>
<body>
</body>
</html>
arr.forEach()
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
arr.forEach((item, index) => {
// console.log('第' + index + '个是：' + item);
console.log(`第${index}个是${item}`);
});
</script>
</head>
<body>
</body>
</html>
arr.map()
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let arr2 = arr.map(item => {
return item * 2;
});
console.log(arr);
console.log(arr2);
</script>
</head>
<body>
</body>
</html>
arr.map2
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let arr2 = arr.map(item => item * 2);
console.log(arr);
console.log(arr2);
</script>
</head>
<body>
</body>
</html>
arr.reduce()
求和
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let result = arr.reduce((tmp, item, index) => {
return tmp + item;
});
console.log(arr);
console.log(result);
</script>
</head>
<body>
</body>
</html>
arr.reduce2
求平均数
<!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>
<script>
let arr = [12, 5, 8, 99, 27, 24, 30, 13];
let result = arr.reduce((tmp, item, index) => {
if (index < arr.length - 1) {
return tmp + item;
} else {
return (tmp + item) / arr.length;
}
});
console.log(arr);
console.log(result);
</script>
</head>
<body>
</body>
</html>
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