replacing variables of an array in a loop

Question

I'm trying to make some sort of cryptographer, and I need to replace for ex. every "a" with "b" when the user asks for it.

if (DoYouWannaCrypt == 1) { binput.forEach(function(v, i) { if(v === "a") { input[i] = "$" } }) };

This works fine, however I want to add another condition that this should only be done for all 5th values of another array.

if (Val is 5th) { if (DoYouWannaCrypt == 1){ binput.forEach(function(v, i) { if(v === "a") { input[i] = "$" } }) } };

I think you can see where I'm stuck at. I need it to work for all 5th values not just the first one.

Please don't use <br> as new lines. Use the markdown to style your post. — ibrahim mahrir
– ibrahim mahrir, Commented Apr 20, 2017 at 21:10
why not ask if i can be evenly divided by 5? syntax is if(i % 5 == 0) — user5328504
– user5328504, Commented Apr 20, 2017 at 21:11
No, I can't see where you're stuck at. What is Val? If binput is your array, your if is in the wrong place. — Heretic Monkey
– Heretic Monkey, Commented Apr 20, 2017 at 21:11
Please read this before posting other posts: stackoverflow.com/help/formatting — ibrahim mahrir
– ibrahim mahrir, Commented Apr 20, 2017 at 21:13
ABove abstraction of the code should work. If something doesn't work, error is probably in your abstraction: (Val is 5th) and we can't see it. Maybe you should post a fiddle — Mirko Vukušić
– Mirko Vukušić, Commented Apr 20, 2017 at 21:13

Jonas Wilms · Accepted Answer · 2017-04-20 21:39:11Z

Thats what map is for:

var crypted=binput.map((l,i)=>(i+1)%5?l:({"a":"$"}[l]||l));

http://jsbin.com/zepewituro/edit?console

Check if index (starting from 0, thats why +1 ) modulo 5 is not 0,then take the letter l, if its 0 ( then we are at the 5*n th position), then we try to replace our letter with another one, if it isnt possible fallback to the letter (||l).

OP didn’t say “for every fifth element of binput”, he said “for every fifth element of another array”.

7vujy0f0hy · Accepted Answer · 2017-04-20 22:16:56Z

Since your code appears irrelevant to your problem, let me store it safely in a function first:

function something(binput, input, DoYouWannaCrypt) { if (DoYouWannaCrypt == 1) binput.forEach(function(v, i) {if (v === "a") input[i] = "$"}); }

If you want to do this operation only for the first element of anotherArray:

for (let Val in anotherArray) if (!Val) something(binput, input, DoYouWannaCrypt);

If you want to do it for every element of anotherArray:

for (let Val in anotherArray) something(binput, input, DoYouWannaCrypt);

If you want to do it for every fifth element of anotherArray:

for (let Val in anotherArray) if (!(Val%5)) something(binput, input, DoYouWannaCrypt);

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