Change index based on the lowest value

Question

Is there a function in JavaScript that allows me to change the index? For example, I have 4 values in an array:

var arr = [10, -20, 20, 30]

Now I want to set the lowest value as the first index and the following after the same pattern. The index should be for the example above:

[-20, 10, 20, 30]

Are you looking for [`Array.prototype.sort()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/sort)? — Patrick Roberts, Dec 26 '18 at 22:16
so what is the question about? sorting? or moving (only) the first element? — Nina Scholz, Dec 26 '18 at 22:33

ic3b3rg · Answer 1 · 2018-12-26T22:25:27.897

2

It sounds like you want to sort the array. The default JS sort uses string-based comparisons. You need to provide your own comparator function for numeric comparisons:

var arr = [10, -20, 20, 30]

arr.sort((i, j) => i - j)

console.log(arr)

edited Dec 26 '18 at 22:25

answered Dec 26 '18 at 22:18

ic3b3rg

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Your sorting method is quite silly when `(i, j) => i - j` suffices, and besides, if this is the answer then there are plenty of duplicates to close this with, no need to answer it again. – Patrick Roberts Dec 26 '18 at 22:21
1

Thanks ic3b3rg "Sort" is what I was looking for. – JCss Dec 26 '18 at 22:25
@PatrickRoberts ok, thanks - that's a better comparator, I updated. – ic3b3rg Dec 26 '18 at 22:25

score 2 · Answer 2 · answered Dec 26 '18 at 22:21

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You could get the index of the smallest value, splice it and unshift this value.

The result does not alter the order of other elements, like with sort.

var array = [10, -20, 20, 30],
    index = array.reduce((r, v, i, a) => a[r] < v ? r : i, 0);

array.unshift(array.splice(index, 1)[0]);

console.log(array);

answered Dec 26 '18 at 22:21

Nina Scholz

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Thanks, Nina, that's also a cool way to do that! – JCss Dec 26 '18 at 22:31

Change index based on the lowest value

2 Answers2