[Vlasenko Fedor]

Мой маленький велосипед

var arr = [73435, 968959, 450300],
    result = arr.reduce(function(prev, el) {
        el = el.toString().split('').sort().join('');
        if (/(\d)\1{2}/.test(el)) {
            prev.push(el.replace(/^.*(\d)\1{2}.*$/, '$1'));
        }
        return prev;
    }, []);
    alert(JSON.stringify(result));

var arr = [73435, 968995988, 450300, 226],
    result = arr.reduce(function(prev, el) {
        el = el.toString().split('').sort().join('');
        if (/(\d)\1{2}/.test(el)) {
            prev.push(el.match(/(\d)\1{2}/g).map(function(val) {
              return val[0];
            }));
        }
        return prev;
    }, []);
    alert(JSON.stringify(result));