标签:spl unicode编码 逗号 个数 有一个 表达 func 目的 let
let arr = ['a','b','c']
let newArr = arr.join('')//参数可以是空格 逗号 连字符等
console.log(newArr)//abc
console.log(arr)//['a','b','c']
let arr = [1,2,3]
arr.push(4)
console.log(arr)//[1,2,3,4]
let arr = ['a','b','c']
arr.pop()
console.log(arr)//["a", "b"]
let arr = ['a','b','c']
arr.shift()
console.log(arr)//["b", "c"]
let arr = ['a','b','c']
arr.unshift('1','2','3')
console.log(arr)//["1", "2", "3", "a", "b", "c"]
let arr = ["1", "2", "3", "a", "b", "c"]
arr.splice(0,1)//["2", "3", "a", "b", "c"]
arr.splice(1,1)//["1", "3", "a", "b", "c"]
arr.splice(-1,1)//["1", "2", "3", "a", "b"]
arr.splice(-2,2)//["1", "2", "3", "a"]
//升序排列
function sortArr(a,b){
return a-b
}
let arr = [1,4,6,2,8,3,9,5,10,7]
console.log(arr.sort(sortArr))//[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
//降序排列
function sortArr(a,b){
return b-a
}
let arr = [1,4,6,2,8,3,9,5,10,7]
console.log(arr.sort(sortArr))//[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]
let arr = [1,2,3,4,5]
arr.reverse()
console.log(arr)//[5, 4, 3, 2, 1]
let arr1 = [1,2,3]
let arr2 = ["a","b","c"]
let arr3 = arr1.concat(arr2)
console.log(arr3)//[1, 2, 3, "a", "b", "c"]
console.log(arr1)//[1,2,3]
console.log(arr2)//["a","b","c"]
let arr = ['a','b','c','d','e','f','g']
arr.slice(1,2)//从索引1开始,到索引2结束,但不包括索引2:["b"]
arr.slice(1,-2)//从索引1开始,到倒数第二个索引结束:["b", "c", "d", "e"]
var arr = ['A', 'B', 'C', 'D', 'E', 'F', 'G'];
var aCopy = arr.slice();
console.log(aCopy)//['A', 'B', 'C', 'D', 'E', 'F', 'G']
5个迭代方法:
currentValue:必需。当前元素
index:可选。当前元素的索引值
arr:可选。当前元素所属的数组对象
thisValue:可选。传递给函数的值一般用 "this" 值.如果这个参数为空, "undefined" 会传递给 "this" 值
语法:
arr.forEach(function(currentValue,index,arr){
//do something
},thisValue)
语法:
arr.map(function(currentValue,index,arr){
//do something
},thisValue)
语法:
arr.map(function(currentValue,index,arr){
//do something
},thisValue)
语法:
arr.map(function(currentValue,index,arr){
//do something
},thisValue)
语法:
arr.some(function(currentValue,index,arr){
//do something
},thisValue)
2个归并方法:reduce()、reduceRight()(原数组不会发生改变)
total :必需。初始值, 或者计算结束后的返回值
cur :必需。当前元素
index :可选。当前元素的索引
arr:可选。当前元素所属的数组对象
initialValue:可选。传递给函数的初始值
语法:
arr.reduceRight(function(total,cur,index,arr){
//do something
}, initialValue)
JavaScript Math 对象方法
基本数据类型:Number、String、Boolean、Null、 Undefined、Symbol(ES6)
引用数据类型:Object
JavaScript中的假值:0 false "" null NaN undefinde
标签:spl unicode编码 逗号 个数 有一个 表达 func 目的 let
原文地址:https://www.cnblogs.com/kaizhadiyishuai/p/11883716.html