Javascript - Index Each Element in an Array/List

Question

> var lst = ['red', 'blue', 'yellow'];
> someFunc(lst);
[('red', 0), ('blue', 1), ('yellow', 2)]

Is there any way to do this in Javascript/JQuery? I know that I can simply just make a for loop and convert each of the original list's element to what I want, but I was wondering if there was a built in way of doing this.

Thanks!

UM, you want objects? nested arrays? That output does not make sense — epascarello
– epascarello, Commented Aug 22, 2016 at 17:20
You mean lst.map(function(v, i) { return { value: v, index: i } } )? — haim770
– haim770, Commented Aug 22, 2016 at 17:21
Something that puts the index to each element, could be objects. — Lawrence Vo
– Lawrence Vo, Commented Aug 22, 2016 at 17:21
Why by the way? lst[0] is red, lst[1] is blue. lst.indexOf("yellow") is 2 — mplungjan
– mplungjan, Commented Aug 22, 2016 at 17:33

Nina Scholz · Accepted Answer · 2016-08-22 17:21:26Z

2

You could use Array#map and return for each item an array with the value and the index.

var lst = ['red', 'blue', 'yellow'],
    array = lst.map(function (a, i) { return [a, i]; });

console.log(array);

answered Aug 22, 2016 at 17:21

Nina Scholz

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2 Comments

Lawrence Vo Over a year ago

Yep! Except the comma should be a semi-colon, right?

Halfpint Over a year ago

No, Nina's declaring two variables, its shorthand for writing var lst ...; var array ...;

haim770 · Accepted Answer · 2016-08-22 17:22:43Z

0

You can leverage the map() function that is providing you both the value and and index of each item in the array:

lst.map(function(v, i) { return { value: v, index: i }; } );

See MDN

answered Aug 22, 2016 at 17:22

haim770

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Comments

kevin ternet · Accepted Answer · 2016-08-22 17:30:28Z

0

With map method in ES6 :

var lst = ['red', 'blue', 'yellow'];
var array = lst.map((item, index) => [item, index])
console.log(array); // [ [ 'red', 0 ], [ 'blue', 1 ], [ 'yellow', 2 ] ]

answered Aug 22, 2016 at 17:30

kevin ternet

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