Question

How to remove the last n occurrences of a substring in a string in JavaScript

Answer 1

// Remove last n occurrences of a substring
function removeLastNOccurrences(s, sub, n) {
    const positions = [];
    let pos = s.indexOf(sub);

    // Find all occurrences
    while (pos !== -1) {
        positions.push(pos);
        pos = s.indexOf(sub, pos + sub.length);
    }

    // Remove from the end
    for (let i = positions.length - 1; i >= 0 && n > 0; i--, n--) {
        const start = positions[i];
        s = s.slice(0, start) + s.slice(start + sub.length);
    }

    return s;
}

// Remove extra spaces (collapse multiple spaces, trim ends)
function removeExtraSpaces(s) {
    return s.trim().split(/\s+/).join(" ");
}

const text = "abc xyz xyz abc xyzabcxyz abc";

const result = removeLastNOccurrences(text, "xyz", 3);
console.log(result);

const cleaned = removeExtraSpaces(result);
console.log(cleaned);


/*
run:

abc xyz  abc abc abc
abc xyz abc abc abc

*/

 

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