LaTherapist

var checkCondition = new Function('a1, b1, a2, b2', 'return ' + condition.value);
if(checkCondition(+(a1.value), +(b1.value), +(a2.value), +(b2.value))){
result.style.backgroundColor = '#b6d7a8';
} else {
result.style.backgroundColor = '#fff';
}