[英]I don't how why my backgroundImage doesn't work
為什么我的橫幅沒有改變她的背景? 請幫我。
當我運行該文件時,控制台告訴我:
未捕獲的類型錯誤:flechedroite.addEventListener 不是函數
我真的不明白。 我是 Javascript 的初學者,所以請用友好的語言向我解釋如何修復此錯誤:)
var flechedroite = document.getElementsByClassName('fa-arrow-right');
var flechegauche = document.getElementsByClassName('switch-left');
var banner = document.getElementById('banner');
var images = [];
var changeBackground = function (bElement, bUrl) {
return bElement.style.backgroundImage = "url(" + bUrl + ")";
}
//image list
images[0] = 'images/image1.jpg';
images[1] = 'images/image2.jpg';
images[2] = 'images/image3.jpg';
flechedroite.addEventListener('click', function() {
for (var i = 0; i < images.length; i++) {
changeBackground(document.body, images[i]);
}
})
JS代碼
var images = [];
var changeBackground = function (bElement, bUrl) {
return bElement.style.backgroundImage = "url("+bUrl+")";
}
//image list
images[0] = 'https://www.gettyimages.ie/gi-resources/images/Homepage/Hero/UK/CMS_Creative_164657191_Kingfisher.jpg';
images[1] = 'https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTOGUhZo0Qe81U5qY_Z-seXgsD79LEEet832TVOlLMOEy10ZPsV';
images[2] = 'https://cdn.pixabay.com/photo/2016/06/18/17/42/image-1465348_960_720.jpg';
window.onload = function(){
var flechedroite = document.getElementsByClassName('fa-arrow-right');
var flechegauche = document.getElementsByClassName('switch-left');
var banner = document.getElementById('banner');
var currentImageIndex = 0;
flechedroite[0].addEventListener('click', function() {
currentImageIndex = (currentImageIndex+1)%images.length;
changeBackground(document.body, images[currentImageIndex]);
})
}
函數 getElementsByClassName 返回一個 HTMLCollection,它是一個類似數組的結構,可以包含多個元素。 所以需要使用索引來訪問其中包含的元素。
所以 flechedroite.addEventListener 導致錯誤但 flechedroite[0].addEventListener 應該工作
https://developer.mozilla.org/en-US/docs/Web/API/Element/getElementsByClassName
如果你使用'getElementsByClassName'並且你想添加一個'addEventListener',你不能以'通用'的方式做到這一點: "flechedroite.addEventListener ('click', function () {}"
。你必須這樣做每個元素:
var flechedroite = document.getElementsByClassName('fa fa-arrow-right');
//flechedroite contains all the elements that have the 'fa fa-arrow-right' classes
//on each element you have to add the "addEventListener"
for (var i = 0; i < flechedroite.length; i++) {
flechedroite[i].addEventListener('click', function() {
alert('flechedroite');
});
}
基本示例JSFiddle1
一個更高級的例子JSFiddle2
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