ボーリングのスコアを求める。初めはリストっぽい感じで書き始めたが1時間くらいで限界を迎えてしかたなく手続きっぽく書いた。

balling.js

var processer = function(s){
    var score = current = i = 0
    ,tokens = s.split('').map(function(t){return (t==='-')?'0':t});
    for(;;i++){
        if(/^\d$/.test(tokens[i])){
            if(!/\/|\d$/.test(tokens[++i])){
                throw new Error("Invalid Input");
            }
            score += tokens[i] === '/' ? 10 + (tokens[i+1]==='X'?10:parseInt(tokens[i+1])) : parseInt(tokens[i]) + parseInt(tokens[i-1]);
        } else if(tokens[i] === 'X'){
            switch(tokens[i+2]){
            case '/':
                score += 20;
                break;
            case 'X':
                score += 30;
                break;
            default:
                score += 10 + ((tokens[i+1]==='X') ? 10:parseInt(tokens[i+1])) + parseInt(tokens[i+2]);
                break;
            }
        } else {
            throw new Error("Invalid Input");
        }
        if(++current == 9){
            ++i;
            break;
        }
    }
    if(tokens[i+2] === undefined ||
       (/^X$/.test(tokens[i]) || (/\X|\//.test(tokens[i+1])) && tokens[i+3] === undefined)){
        for(;i<tokens.length;i++){
            score += tokens[i] === 'X'?10:tokens[i] === '/'?10-parseInt(tokens[i-1]):parseInt(tokens[i]);
        }
        return score;
    }
    throw new Error("Invalid Input");
};

var printTest = function(testCase, result){
    var actual = processer(testCase);
    console.log('test case : ' + testCase + ' ' +
                (actual === result ? 'success' : 'failed should : ' + result + ' actual : ' + actual));
};

[["--------------------", 0],
 ["9-9-9-9-9-9-9-9-9-9-", 90],
 ["X54----------------", 28],
 ["1/5-----------------", 20],
 ["1/5-2/-/8-----------", 56],
 ["------XX----------", 30],
 ["------XXX--------", 60],
 ["XXXXXXXXXXXX", 300],
 ["-------------------/5", 15],
 ["------------------X54", 19],
 ["5/5/5/5/5/5/5/5/5/5/5", 150]].forEach(function(a){
     printTest.apply(null, a);
 });