Array splice with unexpected results

Question

Trying to understand Array.splice().

deleteCount: An integer indicating the number of old array elements to remove.

Ok. Seems straightforward. I want to remove the last 4 objects in the array. I hope that's the same as elements?

arr.splice(<start>, deleteCount<how-many-to-remove>):


// {0 - 8} is an example of object position
let obArr = [{0}, {1}, {2}, {3}, {4}, {5}, {6}, {7}]

// Start from the last and remove four:
obArr.splice(-1, 4)

console.log(obArr) // not expected.

console.log(obArr) // expected: [{0}, {1}, {2}, {3}]

Don't use splice at all, it is considered a bad practice. Instead use array.slice and it's not python so -1 won't work in slice as well. — Zydnar
– Zydnar, Commented Dec 10, 2018 at 16:30
@MarkMeyer it's not what I mean, it will simply work the same way, but it won't change obArr so it's not what OP wants. — Zydnar
– Zydnar, Commented Dec 10, 2018 at 16:36

Mark · Accepted Answer · 2018-12-10 16:29:07Z

5

Your code starts at the last item and tries to remove four values after the last item. But there aren't four values after the last item. If you want to remove four from the end start earlier in the array:

let obArr = [0, 1, 2, 3, 4, 5, 6, 7]

// Start from the 4th last and remove four:
obArr.splice(-4, 4)

console.log(obArr)

answered Dec 10, 2018 at 16:29

Mark

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1 Comment

Sylar Over a year ago

Readability is now understandable "Start from the 4th last and remove four". Many thanks

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