javascript - 从jQuery 1迁移到jQuery 3(Migrating from jQuery 1 to jQuery 3)

Question

I bought an HTML template only to find it uses jQuery 1. I am trying to upgrade to jQuery 3 but I have an issue with this piece of code in the template's main.js file:(我买了一个HTML模板，只是发现它使用jQuery1。我正在尝试升级到jQuery 3，但是模板的main.js文件中的这段代码存在问题：)

var background_image = function() {
    $("[data-bg-img]").each(function() {
        var attr = $(this).attr('data-bg-img');
        if (typeof attr !== typeof undefined && attr !== false && attr !== "") {
            $(this).css('background-image', 'url('+attr+')');
        }
    });  
};

The HTML part this references is:(此引用的HTML部分是：)

 <figure class="deal-thumbnail embed-responsive embed-responsive-16by9" data-bg-img="'.$dealimage.'">

This stopped working when upgrading to jQuery 3.4.1.(升级到jQuery 3.4.1时，此操作停止了。)

Not sure what to do.(不知道该怎么办。) I would appreciate any help I can get.(我将不胜感激。)

CSS:(CSS：)

*[data-bg-img] {
    background-position: center;
    background-repeat: no-repeat;
    -webkit-background-size: cover;
   -moz-background-size: cover;
   -o-background-size: cover;
   background-size: cover;
 }

  ask by Bruno translate from so

Answer 1

It turns out I overlooked the most basic document.ready function, which meant the script didn't even run.(事实证明，我忽略了最基本的document.ready函数，这意味着脚本甚至没有运行。)

In jQuery 1.xx it was written as:(在jQuery 1.xx中，其编写为：)

$(document).on('ready', function() {

})

I changed it to:(我将其更改为：)

$(document).ready(function() {

})