ts-project-builder/src/utils/rollup/browser-path.ts

Rollup-based TypeScript builder with multi-format output and built-in common plugins.

const ANY_SLASH_REGEX = /[/\\]/;

export function relative(from: string, to: string) {
    const fromParts = from.split(ANY_SLASH_REGEX).filter(Boolean);
    const toParts = to.split(ANY_SLASH_REGEX).filter(Boolean);

    if (fromParts[0] === '.') fromParts.shift();
    if (toParts[0] === '.') toParts.shift();

    while (fromParts[0] && toParts[0] && fromParts[0] === toParts[0]) {
        fromParts.shift();
        toParts.shift();
    }

    while (toParts[0] === '..' && fromParts.length > 0) {
        toParts.shift();
        fromParts.pop();
    }

    while (fromParts.pop()) {
        toParts.unshift('..');
    }

    return toParts.join('/');
}