一:数组方法filter(过滤)
1:过滤掉不能被3整除的数,打印出来能被整除的数
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
//过滤器filter
let arr = [12, 33, 66, 99, 5]
let result = arr.filter(item => {
if (item % 3 == 0) {
return true;
} else {
return false;
}
})
console.log(result)
</script>
</html>
打印结果如下:
或者这样写,效果是一样的
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
let arr = [11, 33, 66, 99, 5]
let result = arr.filter(item => {
return item % 3 == 0;
})
console.log(result)
</script>
</html>
打印结果如下:
2:过滤商品价格小于10000元的商品,打印大于10000元的商品
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
//商品列表
let arr = [{
title: '笔记本电脑',
price: 12033
},
{
title: '智能音箱',
price: 99
},
{
title: '鼠标',
price: 33
},
{
title: '单反摄像机',
price: 20000
},
]
let result = arr.filter(item => item.price >= 10000);
console.log(result)
</script>
</html>
打印结果如下:
二:数组方法map(映射)
一般写法
//一般写法
let arr=[12,5,8];
let result= arr.map(function(item){
return item*2;
})
console.log(result)
箭头函数写法
//箭头函数
let arr=[10,5,8];
let result= arr.map(item=>{
return item*2;
})
console.log(result)
去掉花括号的写法(只有一个return的时候,{}可以省略)
let arr=[10,5,9];
let result=arr.map(item=>item*2);
console.log(result)
示例:判断数组所对应的的状态是否及格
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
let scroe = [12, 77, 88, 99, 33, 100, 59];
let result = scroe.map(item => item >= 60 ? '及格' : '不及格');
console.log(scroe)
console.log(result)
</script>
</html>
三:数组方法reduce和forEach
1:reduce应用场景:计算数组中所有值的总和
数组求和:
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
//一堆变成一个,算总数
let arr = [12, 33, 66, 99]
let result = arr.reduce(function(tmp, item, index) {
return tmp + item
})
console.log(result);
</script>
</html>
打印结果如下:
2:forEach循环遍历(迭代)
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
let arr = [12, 4, 6, 89, 2]
arr.forEach(item => {
console.log(item)
})
</script>
</html>
打印结果如下:
参数index
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
</body>
<script>
let arr = [12, 4, 6, 89, 2]
//参数index
arr.forEach((item,index) => {
console.log(index+ ':' +item)
})
</script>
</html>
打印结果如下:
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