0
當我遍歷由querySelectorAll獲得的節點列表併爲每個節點添加一個新類時,它比getElementsByClassName(100ms)獲得的時間(3ms)少得多。爲什麼?querySelectorAll vs getElementsByClassName
var container = document.getElementById('box-container');
var button = document.getElementById('button');
for (var i = 0; i < 3000; i++) {
var div = document.createElement('div');
div.classList.add('box');
div.index = i;
container.appendChild(div);
}
button.addEventListener('click', function() {
var box1 = container.getElementsByClassName('box');
for (var i = 1;i < box1.length; i+=2){
box1[i].classList.toggle('gray');
};
var box2 = container.querySelectorAll('.box');
for (var i = 1;i < box2.length; i+=2){
box2[i-1].classList.toggle('gray');
};
});