【JS】721- 15個必須知道的JavaScript數(shù)組方法

1.some() 2. reduce() 3. Every() 4. map() 5. flat() 6. filter() 7. forEach() 8. findIndex() 9. find() 10. sort() 11. concat() 12. fill() 13. includes() 14. reverse() 15. flatMap()
注意,大多數(shù)情況下,我們將簡化作為參數(shù)傳遞的函數(shù)。
//?Instead?of?using?this?waymyAwesomeArray.some(test => { if (test === "d") { return test }})// We'll use the shorter onemyAwesomeArray.some(test => test === "d")
1、some()
const?myAwesomeArray?=?["a",?"b",?"c",?"d",?"e"]myAwesomeArray.some(test => test === "d")//------->?Output?:?true
2、reduce()
const?myAwesomeArray?=?[1,?2,?3,?4,?5]myAwesomeArray.reduce((total, value) => total * value)//?1?*?2?*?3?*?4?*?5//------->?Output?=?120
3、Every()
const?myAwesomeArray?=?["a",?"b",?"c",?"d",?"e"]myAwesomeArray.every(test => test === "d")// ------->?Output?:?falseconst?myAwesomeArray2?=?["a",?"a",?"a",?"a",?"a"]myAwesomeArray2.every(test => test === "a")//------->?Output?:?true
4、map()
const myAwesomeArray = [5, 4, 3, 2, 1]myAwesomeArray.map(x => x * x)//------->?Output?:?25//??????????????????16//??????????????????9//??????????????????4//??????????????????1
5、flat()
const myAwesomeArray = [[1, 2], [3, 4], 5]myAwesomeArray.flat()//------->?Output?:?[1,?2,?3,?4,?5]
6、filter()
const myAwesomeArray = [ { id: 1, name: "john" },{ id: 2, name: "Ali" }, { id: 3, name: "Mass" },{ id: 4, name: "Mass" },]myAwesomeArray.filter(element => element.name === "Mass")//------->?Output?:?0:{id:?3,?name:?"Mass"},//??????????????????1:{id:?4,?name:?"Mass"}
7、forEach()
const myAwesomeArray = [ { id: 1, name: "john" },{ id: 2, name: "Ali" }, { id: 3, name: "Mass" },]myAwesomeArray.forEach(element => console.log(element.name))//------->?Output?:?john//??????????????????Ali//??????????????????Mass
8、?findIndex()
const myAwesomeArray = [ { id: 1, name: "john" },{ id: 2, name: "Ali" }, { id: 3, name: "Mass" },]myAwesomeArray.findIndex(element => element.id === 3)//?------->?Output?:?2myAwesomeArray.findIndex(element => element.id === 7)//------->?Output?:?-1
9、?find()
const myAwesomeArray = [ { id: 1, name: "john" },{ id: 2, name: "Ali" }, { id: 3, name: "Mass" },]myAwesomeArray.find(element => element.id === 3)//?------->?Output?:?{id:?3,?name:?"Mass"}myAwesomeArray.find(element => element.id === 7)//------->?Output?:?undefined
10、?sort()
const?myAwesomeArray?=?[5,?4,?3,?2,?1]//?Sort?from?smallest?to?largestmyAwesomeArray.sort((a, b) => a - b)// ?------->?Output?:?[1,?2,?3,?4,?5]//?Sort?from?largest?to?smallestmyAwesomeArray.sort((a, b) => b - a)//------->?Output?:?[5,?4,?3,?2,?1]
11、?concat()
const myAwesomeArray = [1, 2, 3, 4, 5]constmyAwesomeArray2 = [10, 20, 30, 40, 50]myAwesomeArray.concat(myAwesomeArray2)//------->?Output?:?[1,?2,?3,?4,?5,?10,?20,?30,?40,?50]
12、?fill()
const?myAwesomeArray?=?[1,?2,?3,?4,?5]//?The?first?argument?(0)?is?the?value//?The?second?argument?(1)?is?the?starting?index//?The?third?argument?(3)?is?the?ending?indexmyAwesomeArray.fill(0, 1, 3)//------->?Output?:?[1,?0,?0,?4,?5]
13、?includes()
const?myAwesomeArray?=?[1,?2,?3,?4,?5]myAwesomeArray.includes(3)//?------->?Output?:?truemyAwesomeArray.includes(8)//?------->?Output?:?false
14、?reverse()
const?myAwesomeArray?=?["e",?"d",?"c",?"b",?"a"]myAwesomeArray.reverse()// ------->?Output?:?['a',?'b',?'c',?'d',?'e']
15、?flatMap()
const myAwesomeArray = [[1], [2], [3], [4], [5]]myAwesomeArray.flatMap(arr => arr * 10)//------->?Output?:?[10,?20,?30,?40,?50]//?With?.flat()?and?.map()myAwesomeArray.flat().map(arr => arr * 10)//------->?Output?:?[10,?20,?30,?40,?50]

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