How to start over when there are no more elements in a loop?

Question

Let's say I "want" 6 elements from an array which only contains 3. If the end is reached, start over.

Example:

let arr = ["a", "b", "c"];
let wanted = 5;

for(let i = 0; i < wanted; i++) {
    console.log(arr[i]);
}

Which of course returns:

a
b
c
undefined
undefined

Instead, I need:

a
b
c
a
b

Is there a way to start from the beginning of the array after the elements are over?

Yeah, I had thought of just resetting it but since the reset is happening in the loop, it never ends. — Laurent, Mar 16 '17 at 08:03
Not exact duplicate but similar: http://stackoverflow.com/questions/17483149/how-to-access-array-in-circular-manner-in-javascript — Rajesh, Mar 16 '17 at 08:07

Pranav C Balan · Accepted Answer · 2017-03-16T14:17:40.770

11

Get the remainder using %(Remainder) operator.

console.log(arr[i % arr.length]);

The remainder value would be within the array index range.

For example: when i reaches to

3 => 3 % 3 = 0
4 => 4 % 3 = 1
0 => 0 % 3 = 0.

let arr = ["a", "b", "c"];
let wanted = 5;

for (let i = 0; i < wanted; i++) {
  console.log(arr[i % arr.length]);
}

edited Mar 16 '17 at 14:17

answered Mar 16 '17 at 08:00

Pranav C Balan

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2

Can you explain exactly what is going on here? – Akshay Khandelwal Mar 16 '17 at 08:02
1

Plus one for the answer, plus one again for calling % the remainder operator. – Bathsheba Mar 16 '17 at 08:03
1

@PranavCBalan Just made you explanation as points. If not required, please revert it. :-) – Rajesh Mar 16 '17 at 08:13

score 2 · Answer 2 · answered Mar 16 '17 at 08:02

2

You can use (%) remainder operator. It will get index started from 0 till arr.length - 1.

First step is

[0 % 3] === 0 whole 0 remainder, 
[1 % 3] === 0 whole 1 remainder,
[2 % 3] === 0 whole 2 remainder
[3 % 3] === 1 whole 0 remainder
[4 % 3] === 1 whole 1 remainder

let arr = ["a", "b", "c"];
let wanted = 5;

for(let i = 0; i < wanted; i++) {
    console.log(arr[i % arr.length]);
}

answered Mar 16 '17 at 08:02

Suren Srapyan

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This is just a stolen answer... http://stackoverflow.com/a/42828321/1990451 – smnbbrv Mar 16 '17 at 08:06
@smnbbrv And how are you sure ? If you will see my other answers you can find similar ones – Suren Srapyan Mar 16 '17 at 08:07
by a timestamp? – smnbbrv Mar 16 '17 at 08:07
if I can find similar ones might be that instead of answering you can mark the question as a duplicate instead of answering? – smnbbrv Mar 16 '17 at 08:08
@smnbbrv I am not going to show or prove you anything. And there is noting to steel. If you name it steeling, so every answer after the first may be considered as a stolen answer. So have a good luck – Suren Srapyan Mar 16 '17 at 08:13
@smnbbrv, What about [be nice](http://stackoverflow.com/help/be-nice) And 2 minute 18 sec – Drag and Drop Mar 16 '17 at 08:14
There are moderators. Write them – Suren Srapyan Mar 16 '17 at 08:15
And istead of witch hunting comes with fact. as the version that include snippet and explanation and not a simple 'do this' came after this post. – Drag and Drop Mar 16 '17 at 08:31

score 0 · Answer 3 · answered Mar 16 '17 at 08:02

0

Just use %

let arr = ["a", "b", "c"];
let wanted = 5;

for(let i = 0; i < wanted; i++) {
    console.log(arr[i % arr.length]);
}

answered Mar 16 '17 at 08:02

steppefox

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score 0 · Answer 4 · edited Mar 16 '17 at 09:02

0

let arr = ["a", "b", "c"];
let wanted = 5;    

for (let i = 0; i < wanted; i++) {
    console.log(arr[i]);
    if (arr.length == i) {
        i = 0;
    }
}

edited Mar 16 '17 at 09:02

darijan

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answered Mar 16 '17 at 08:02

codeGig

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As far as I can understand, this loop is infinite if `arr.length < wanted` – default locale Mar 16 '17 at 08:58

Elie Nassif · Answer 5 · 2017-03-16T08:56:11.927

0

if (i+1 == arr.length){
 console.log(arr[i]);
 i=0;
 wanted =wanted-arr.length;
}else{
 console.log(arr[i]);
}

the loop will work normally until your counter is at the last element, then it will be reset to 0 to start over and will keep doing this until you have reached your wanted number of elements.

edited Mar 16 '17 at 08:56

answered Mar 16 '17 at 08:05

Elie Nassif

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what will this code do? Why will it solve, if it does. Please explain – Rajesh Mar 16 '17 at 08:07
Your code spells i in both upper and lowercase, and is lacking a for loop. – tomysshadow Mar 16 '17 at 08:54
oh please give me a break, OP can add the snippet in their code no need to re-write his loop. – Elie Nassif Mar 16 '17 at 08:55

How to start over when there are no more elements in a loop?

5 Answers5