1 let arr = [1,2,3,4,5] 2 console.log(arr.push(6,7)) // 73 console.log(arr) // [1,2,3,4,5,6,7]
1 let arr = [1,2,3,4,5]2 console.log(arr.pop()) // 53 console.log(arr) // [1,2,3,4]
1 let arr = [1,2,3,4,5]2 console.log(arr.shift()) // 13 console.log(arr) // [2,3,4,5]
1 let arr = [1,2,3,4,5]2 console.log(arr.unshift(6,7)) // 73 console.log(arr) // [6,7,1,2,3,4,5]
参数:index 索引值,num 个数
1 let arr = [1,2,3,4,5]2 console.log(arr.splice(2,3)) // [3,4]3 console.log(arr) // [1,2,5]
let str = '12345'console.log(str.split('')) // ["1","2","3","4","5"]
let str1 = '1/2/3/4/5'
console.log(str1.split('/')) // ["1","2","3","4","5"]
1 let arr = [1,2,3,4,5]2 console.log(arr.concat([6,7])) // [1,2,3,4,5,6,7]3 console.log(arr) // [1,2,3,4,5]
1 let arr = [40,8,10,5,79,3]2 console.log(arr.sort()) // [10,3,40,5,79,8]3 4 let arr2 = arr.sort((a,b) => a - b)5 console.log(arr2) // [3,5,8,10,40,79]6 7 let arr3 = arr.sort((a,b) => b - a)8 console.log(arr3) // [79,40,10,8,5,3]
1 let arr = [1,2,3,4,5]2 console.log(arr.reverse()) // [5,4,3,2,1]3 console.log(arr) // [5,4,3,2,1]
1 let arr = [1,2,3,4,5]2 console.log(arr.slice(1,3)) // [2,3]3 console.log(arr) // [1,2,3,4,5]
1 let arr = [1,2,3,4,5] 2 arr.forEach((value, index, array) => { 3 console.log(`value--${value} index--${index} array--${array}`) 4 }) 5 6 // value--1 index--0 array--1,2,3,4,5 7 // value--2 index--1 array--1,2,3,4,5 8 // value--3 index--2 array--1,2,3,4,5 9 // value--4 index--3 array--1,2,3,4,510 // value--5 index--4 array--1,2,3,4,5
1 let arr = [1,2,3,4,5]2 arr.map( (value, index, array)=>{3 value = value * 24 }) 5 console.log(arr) // [1,4,6,8,10]
1 let arr = [1,2,3,4,5]2 let arr2 = arr.filter((value, index) => value >2)3 console.log(arr2) // [3,4,5]
1 let arr = [1,2,3,4,5]2 3 let arr2 = arr.every((value, index) => i > 2)4 console.log(arr2) // false5 6 let arr3 = arr.every((value, index) => i > 0)7 console.log(arr3) // true
1 let arr = [1,2,3,4,5]2 3 let arr2 = arr.some((value, index) => i > 2)4 console.log(arr2) // true5 6 let arr3 = arr.some((value, index) => i > 5)7 console.log(arr3) // false
1 let arr = [1,2,3,4,5,4]2 3 let arr2 = arr.indexOf(4)4 console.log(arr2) // 35 6 let arr3 = arr.indexOf(6)7 console.log(arr3) // -1
1 let arr = [1,2,3,4,5,4]2 3 let arr2 = arr.lastIndexOf(4)4 console.log(arr2) // 55 6 let arr3 = arr.lastIndexOf(6)7 console.log(arr3) // -1
1 let str = '12345'2 console.log(Array.from(str)) // ["1", "2", "3", "4", "5"]3 4 let obj = {0:'a',1:'b',length:2}5 console.log(Array.from(obj)) // ["a", "b"]
1 let str = '11'2 console.log(Array.of(str)) // ['11']3 4 等价于 5 console.log(new Array('11')) // ['11]
ps:
new Array()有缺点,就是参数问题引起的重载
console.log(new Array(2)) // [empty × 2] 是个空数组
console.log(Array.of(2)) // [2]
1 let arr = [1,2,3,4,5,2,4]2 let arr2 = arr.find((value, index, array) => value > 2)3 console.log(arr2) // 3
1 let arr = [1,2,3,4,5]2 let arr1 = arr.findIndex((value, index, array) => value > 2)3 console.log(arr1) // 2
let arr = [1,2,3,4,5]let arr2 = arr.includes(2) console.log(arr2) // turelet arr3 = arr.includes(9) console.log(arr3) // falselet arr4 = [1,2,3,NaN].includes(NaN)console.log(arr5) // true
参数: target – 待填充的元素
start – 开始填充的位置 - 索引
end – 终止填充的位置 - 索引(不包括该位置)
let arr = [1,2,3,4,5]let arr2 = arr.fill(5)console.log(arr2) // [5, 5, 5, 5, 5]console.log(arr) // [5, 5, 5, 5, 5]let arr3 = arr.fill(5,2)console.log(arr3) // [1,2,5,5,5]let arr4 = arr.fill(5,1,3)console.log(arr4) // [1,5,5,4,5]
1 let arr = [1,2,3,4,5]2 let arr2 = arr.keys()3 for (let key of arr2) {4 console.log(key) // 0,1,2,3,45 }
let arr = [1,2,3,4,5]let arr1 = arr.values()for (let val of arr1) { console.log(val); // 1,2,3,4,5}
1 let arr = [1,2,3,4,5]2 let arr2 = arr.entries()3 for (let e of arr2) {4 console.log(e); // [0,1] [1,2] [2,3] [3,4] [4,5]5 }
entries() 方法返回迭代数组。
迭代数组中每个值 前一个是索引值作为 key, 数组后一个值作为 value。
参数: target --必选 索引从该位置开始替换数组项
start --可选 索引从该位置开始读取数组项,默认为0.如果为负值,则从右往左读。
end --可选 索引到该位置停止读取的数组项,默认是Array.length,如果是负值,表示倒数
1 let arr = [1,2,3,4,5,6,7] 2 3 let arr2 = arr.copyWithin(1) 4 console.log(arr2) // [1, 1, 2, 3, 4, 5, 6] 5 6 let arr3 = arr.copyWithin(1,2) 7 console.log(arr3) // [1, 3, 4, 5, 6, 7, 7] 8 9 let arr4 = arr.copyWithin(1,2,4)10 console.log(arr4) // [1, 3, 4, 4, 5, 6, 7]
1 let a = 1234 2 let b = "fsaufh" 3 let c = {a:1,b:2} 4 let d = [1,2] 5 6 let mark1 = Array.isArray(a) 7 console.log(mark1) // false 8 9 let mark2 = Array.isArray(b)10 console.log(mark2) // false11 12 let mark3 = Array.isArray(c)13 console.log(mark3) // false14 15 let mark4 = Array.isArray(d)16 console.log(mark4) // true
1 let arr = [1,2,3,4,5]2 console.log(arr.join()) // 1,2,3,4,5
3 console.log(arr.join("")) // 123454 console.log(arr.join("-")) // 1-2-3-4-5
参数:pliy表示拉平的层数,默认是1层,想无限拉平可以传入Infinity关键字
1 let arr = [1, 2, [3, [4, 5]]]2 console.log(arr.flat(2)) // [1, 2, 3, 4, 5]3 4 let arr2 = [1,[2,[3,[4,5]]]]5 console.log(arr2.flat(Infinity)) // [1,2,3,4,5]
1 // 相当于 [[2, 4], [3, 6], [4, 8]].flat()2 [2, 3, 4].flatMap((x) => [x, x * 2])3 // [2, 4, 3, 6, 4, 8]
1 let arr = ["Banana", "Orange", "Apple", "Mango"]2 console.log(arr.toString()) // Banana,Orange,Apple,Mango
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