Pure JavaScript
html
1<!DOCTYPE HTML>
2<html lang="ja">
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 </head>
7 <body>
8 <div id="header_pages">
9
10 </div>
11 <script type="text/javascript">
12 window.onload = function () {
13 var header_pages = document.getElementById('header_pages');
14 header_pages.style.width = '100%';
15 header_pages.style.height = '650px';
16 header_pages.style.backgroundImage = 'url(http://dummyimage.com/600x400/000/fff)';
17 header_pages.style.backgroundRepeat = 'no-repeat';
18 header_pages.style.backgroundSize = 'contain';
19 };
20 </script>
21 </body>
22</html>
jQuery
html
1<!DOCTYPE HTML>
2<html lang="ja">
3 <head>
4 <meta charset="UTF-8">
5 <title></title>
6 </head>
7 <body>
8 <div id="header_pages">
9
10 </div>
11 <script src="//code.jquery.com/jquery-2.2.4.min.js"></script>
12 <script type="text/javascript">
13 $(function () {
14 $("#header_pages").css({
15 width: '100%'
16 , height: '650px'
17 , backgroundImage: 'url(http://dummyimage.com/600x400/000/fff)'
18 , backgroundRepeat: 'no-repeat'
19 , backgroundSize: 'contain'
20 });
21 });
22 </script>
23 </body>
24</html>