创建php文件

<?php
$json_string = file_get_contents('https://cn.bing.com/HPImageArchive.aspx?format=js&idx=0&n=1&mkt=zh-CN');
$data = json_decode($json_string, true);
$url_ = 'https://cn.bing.com'.$data['images'][0]['url'];
header("Location: {$url}"); 
?>

加入js文件调用

const backgroundImage = 'url("/bing.php")';
$("#app")[0].style.backgroundImage = backgroundImage;