I want to split an array and splice it based on some pattern inside the array

Question

Hello I couldn't figure out how to do this,

Let's say I have an array like this

main = [ "1","2","A","4","5","B","6","7","A","8","9","B","10"];

I want to get a new array with result

main2 = ["A","4","5","B","A","8","9","B"] 

and finally break them apart like the following;

main3 = ["A","4","5","B"]     
main4 = ["A","8","9","B"]

As you can see I am taking out the array items from A-B that happened twice.

Answer 1

You could reduce the array into arrays, starting with a certain value and ending with another.

const
    start = 'A',
    end = 'B',
    data = ["1", "2", "A", "4", "5", "B", "6", "7", "A", "8", "9", "B", "10"],
    result = data.reduce((r, v) => {
        if (v === start) { r.push([v]); return r; }
        const last = r[r.length - 1];
        if (last?.length && last[last.length - 1] !== end) last.push(v);
        return r;
    }, []);

console.log(result);

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Another approach

const
    start = 'A',
    end = 'B',
    data = ["1", "2", "A", "4", "5", "B", "6", "7", "A", "8", "9", "B", "10"],
    result = [];

let i = data.indexOf(start);

while (i !== -1) {
    let j = data.indexOf(end, i + 1);
    result.push(data.slice(i, ++j));
    i = data.indexOf(start, j);
}

console.log(result);

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