Filter Specific Numbers and Sum Up-CodePudding

Given:

I have an array that looks like this:

[1, 1, 3, 3, 3, 2, 2, 1, 3, 3, 2, 3, 4, 2, 3, 4, 4, 2, 1, 3, 2, 4, 3, 2];

What I need:

scoreN = sum up all numbers with one
scoreST = sup all numbers with two
scoreO = sum up all numbers with three
scoreAA = sum up all numbers with four
totalScore = scoreN   scoreST   scoreO   scoreAA

Question:

What is the simplest (beginner friendly) JS code to filter the numbers and get the sum?

const array = [1, 1, 3, 3, 3, 2, 2, 1, 3, 3, 2, 3, 4, 2, 3, 4, 4, 2, 1, 3,2, 4, 3, 2];

Something like?

const scoreN = array.filter(1);
const scoreST = array.filter(2);
const scoreO = array.filter(3);
const scoreAA = array.filter(4);

const totalScore = scoreN   scoreST   scoreO   scoreAA

CodePudding user response：

Your approach was quite correct.

But the array method filter takes a function which you can express with a lambda function x => x === 1 in which the argument x represents the current array value. The return value should be a boolean, in this case we want all numbers equal to 1.

The function reduce takes 2 arguments a function with the previous value and the current value and a default value if the array is empty. In this case 0 if there are no elements to sum up.

const numbers = [1, 1, 3, 3, 3, 2, 2, 1, 3, 3, 2, 3, 4, 2, 3, 4, 4, 2, 1, 3, 2, 4, 3, 2];

const sum = (a, b) => a   b;

const scoreN = numbers.filter(x => x === 1).reduce(sum, 0);
const scoreST = numbers.filter(x => x === 2).reduce(sum, 0);
const scoreO = numbers.filter(x => x === 3).reduce(sum, 0);
const scoreAA = numbers.filter(x => x === 4).reduce(sum, 0);

const total = scoreN   scoreST   scoreO   scoreAA;

console.log(total);

CodePudding user response：

Yep, using filter you can filter the arrays down. However if you use reduce then you can filter and sum at the same time. E.g.:

const scoreN = numbers.reduce((sum, val) => {
    if (val === 1) {
        sum  = val;
    }
    return sum;
}, 0);

CodePudding user response：

The most beginner friendly code, that works the same for most c-like languages would be:

function score(array, value) {  
    let sum = 0;
    for (let i = 0; i < array.length; i  ) {
        let element = array[i];
        if (element === value) {
            sum  = element;
        }
    }
    return sum;
}

another solutions that makes use of JS array functions would be:

function score(array, value) {
    let sum = array
        .filter(e => e === value)
        .reduce((prev, curr) => prev   curr, 0);
    return sum;
}

you would use both functions the same way:

const scoreN = score(array, 1);
const scoreST = score(array, 2);
const scoreO = score(array, 3);
const scoreAA = score(array, 4);

const totalScore = scoreN   scoreST   scoreO   scoreAA;