Get an element of array and add to other elements in Javascript

Question

I have two arrays with same length. I want to get an element from one array and continue adding its value (+1) to each other elements until value is 0.

Here is my code:

const update = (source, target, index) => {
    const keys = Object.keys(source)
    let value = source[target][index]
    source[target][index] = 0
    while (value--) {
        source[target][index++]++
        if (index === source[target].length) {
            index = 0
            target = keys[(keys.indexOf(target) + 1) % keys.length]
        }
    }
    return source
}

console.log(update({a: [0, 0, 0, 8, 0], b: [0, 0, 0, 0, 0]}, 'a', 3))

answer: { a: [ 1, 0, 0, 1, 1 ], b: [ 1, 1, 1, 1, 1 ] }

So what it does is that;

it takes index 3 of Array a which is 8 --> a[3] became 0
continue adding (+1) to itself and other elements of both arrays until a[3] is over.

But here is the challenge, I want to pass by the last element of other array(could be array a or b) and never add +1. So my answer should be:

answer: { a: [ 1, 1, 0, 1, 1 ], b: [ 1, 1, 1, 1, 0 ] } --> last element of b not changed!

would update({a: [0, 0, 0, 8, 0], b: [13, 0, 0, 0, 0]}, 'a', 6) take 13? — Vulwsztyn
– Vulwsztyn, Commented Mar 8, 2022 at 20:21
No! since a.length = 5. But if you want to use 13 then u should call update({a: [0, 0, 0, 8, 0], b: [13, 0, 0, 0, 0]}, 'b', 0) — Angels
– Angels, Commented Mar 8, 2022 at 20:24

Vulwsztyn · Accepted Answer · 2022-03-09 10:16:58Z

1

const update = (source, target_param, index_param) => {
    const keys = Object.keys(source)
    let target = target_param
    let index  = index_param
    let value = source[target][index]
    source[target][index] = 0
    while (value--) {
        source[target][index++]++
        if (index === source[target].length || target !== target_param && index === source[target].length - 1) {
            index = 0
            target = keys[(keys.indexOf(target) + 1) % keys.length]
        }
    }
    return source
}

console.log(update({a: [0, 0, 0, 8, 0], b: [0, 0, 0, 0, 0]}, 'a', 3))

The most important change being the condition (index === source[target].length || target !== target_param && index === source[target].length - 1) and not mutating the function params.

I strongly suggest never mutating the function parameters.

answered Mar 9, 2022 at 10:16

Vulwsztyn

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2 Comments

Angels Over a year ago

Thanks, What do you mean by saying (never mutating the function parameters)? Any mistake in my code?

Vulwsztyn Over a year ago

Not per se. I mean not to change values of the variables that are parameters of the function (those in parentheses at the function declaration). It is an opinion, but I strongly recommend it. BTW you can +1 my ans and mark it as solving if it is solving.

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