//length 可变
var arr = []
arr.length = 10
arr[1] = 2
console.log(arr)
arr.length = 8
console.log(arr)
//index 可以超过length
arr[12] = "f"
console.log(arr)
//push/pop 从尾部读取
arr = [1, 2, 3, 4, 5, 6]
arr.push(12)
console.log(arr)
let a = arr.pop()
console.log(a, arr)
arr.push(...["a", "b", "c"])
console.log(arr)
//shift /unshift 从顶部移除添加
arr.shift()
console.log(arr)
arr.unshift("1", ...[10, "l"])
console.log(arr)
//splice 截取并插入
let arrnew = arr.splice(0, 3, "new", "new1")
console.log(arrnew, "\\n", arr)
//reverse 逆序
arr.reverse()
console.log(arr)
//sort 排序
arr.splice(0, 3)
arr.sort()
console.log(arr)
//new
//arr=new Array()
//Object.values Object.keys Object.entries 取值 取key 数据[[key,value]]
console.log(Object.values(arr))
console.log(Object.keys(arr))
console.log(Object.entries(arr))
let str = "1,2,34,56,,"
arr = str.split(",")
console.log(arr)
//concat 数组连接 返回连接后的数组
arr = arr.concat("new", ...["a", "b", 'c'])
console.log(arr)
//slice
arr1 = arr.slice(1, 3)
console.log(arr1)
//map 类似于foreach
arr.map((v, k, e) => console.log(v))
//求平方
temp = [1, 2, 3]
temp = temp.map(v => v * v)
console.log(temp)
arr.map((v, k) => console.log(`${k}==${v}`))
//filter 筛选
console.log(arr)
arr = arr.filter((v, k) => v > 1)
// arr.filter((v, k) => v > 1).forEach((v, k, s) => {
// console.log(s)
// })
console.log(arr)
//every 是否所有满足条件
console.log("is null:", arr.every(v => !v))
//some 是否有一个满足
console.log("have >1:", arr.some(v => v > 1))
// includes 包含
console.log("hava 2:", arr.includes('2'))
//foreach 与map 区别 map 会返回新数组
console.log(arr)
arr.forEach(v => v * v)
console.log(arr)
//reduce 累加器
arr = arr.map(v => parseInt(v))
let total = arr.reduce((base, num) => base + num, 3)
console.log(total)
// arr = ["apple", "orange", "apple", "orange", "pear", "orange"];
// function getWordCnt() {
// return arr.reduce(function (prev, next) {
// prev[next] = (prev[next] + 1) || 1;
// return prev;
// }, {});
// }
// console.log(getWordCnt());
//find
let t = arr.find(v => v = 2)
console.log(t)
let index = arr.indexOf(34)
console.log(index)
str = arr.join(',')
console.log(str)
node 数组常用方法
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转载自blog.csdn.net/qq_27119625/article/details/85841598
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