I can't understand why IndexOf returned -1-PHP Chinese Network Q&A

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I can't understand why IndexOf returned -1

P粉031492081 2023-09-14 20:02:21

502

I have an array of numbers containing 1-20. When I use the indexOf method to try to find the position of "2", it shows up at the 3rd position (correct).

I have a variable calledday = 2. When I use the code ofarray.indexOf(day), it returns-1.

Why does this happen?

P粉031492081

reply all (1)

P粉5170907482023-09-15 16:50:31 1 floor

function indexofnotworking() { let arr = [...new Array(20).keys()];//creat arr of numbers from 0 -19 let arr1 = arr.slice().reverse();//make a copy and reverse it [...Array.from(new Array(5).keys(), x => x + 5)].forEach(n => { console.log('arr: %s n: %s index: %s', JSON.stringify(arr), n, arr.indexOf(n));//find the indexof n in both arrays console.log('arr1: %s n: %s index: %s', JSON.stringify(arr1), n, arr1.indexOf(n));/display results }) } 11:40:22 AM Info arr: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] n: 5 index: 5 11:40:22 AM Info arr1: [19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0] n: 5 index: 14 11:40:22 AM Info arr: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] n: 6 index: 6 11:40:22 AM Info arr1: [19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0] n: 6 index: 13 11:40:22 AM Info arr: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] n: 7 index: 7 11:40:22 AM Info arr1: [19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0] n: 7 index: 12 11:40:22 AM Info arr: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] n: 8 index: 8 11:40:22 AM Info arr1: [19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0] n: 8 index: 11 11:40:22 AM Info arr: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] n: 9 index: 9 11:40:22 AM Info arr1: [19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3,2,1,0] n: 9 index: 10