window.addEventListener('load',()=> {
allClass(0.4);  // время transition
function allClass(transition){
    let question = document.querySelectorAll('.question'),
    answer = document.querySelectorAll('.answer'),
    arrayHeight = [];
    const props = el => el.getBoundingClientRect();
    [...question].forEach((e,i) => {
        arrayHeight[i] = props(answer[i]).bottom - props(answer[i]).top + 10 + 'px';
        answer[i].style.height = '0px';
        setTimeout(()=> answer[i].style.transition = transition + 's', 50);
        e.addEventListener('click',() => {
            [...answer].forEach((e,i) => { answer[i].style.height = '0px'; });
            props(answer[i]).height == 0 ? answer[i].style.height = arrayHeight[i] : '';
        });
    });
}
},false);

var answer = document.querySelectorAll('.answer');
[].forEach.call(answer, function(item) { item.style.height = '0px'; });

NodeList.prototype.forEach = Array.prototype.forEach; 
//...
answer.forEach(function(e,i){
//...
question.forEach(function(e,i){