longestAbsolutePath.js

const lengthLongestPath = input => {
    return input.split('\n').reduce((os, path) => {
        const idx = path.lastIndexOf('\t') + 1;
        
        idx <= os.filePath.length && os.filePath.splice(idx);
        os.filePath.push(path.slice(idx));
        
        if (path.lastIndexOf('.') >= 0) {
            const length = os.filePath.join('/').length;
            os.longest = length > os.longest ? length : os.longest;
        }
        
        return os;
    }, { filePath: [], longest: 0 }).longest;
};