带有Javascript和CSS的随机背景生成器

Question

I'm trying to make the background change randomly when coming to my site. 我试图在进入网站时随机更改背景。

I saved some images as 1.jpg, 2.jpg etc and I tried to do a bit of javascript random. 我将一些图像另存为1.jpg，2.jpg等，然后尝试随机执行一些javascript。 Can any one suss why this would not work? 谁能猜到为什么这行不通？ I know you won't be able to see the photos, but any help would be great. 我知道您将无法看到这些照片，但是任何帮助都会很棒。

Here is the jsbin - notice the background is selected in #topContainer in css 这是jsbin-注意在CSS的#topContainer中选择了背景

https://jsbin.com/qodukozuqi/edit?html,output https://jsbin.com/qodukozuqi/edit?html,output

<script type="text/javascript">

  function randomBackground () {

    var randomPicture = [Math.floor(Math.random() * 4)+ '.jpg'];
  }
  return randomPicture;

</script>

Here is the full code: 这是完整的代码：

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <!-- The above 3 meta tags *must* come first in the head; any other head content must come *after* these tags -->

    <script type="text/javascript">
  WebFontConfig = {
    google: { families: [ 'Tenor+Sans::latin', 'Rock+Salt::latin' ] }
  };
  (function() {
    var wf = document.createElement('script');
    wf.src = ('https:' == document.location.protocol ? 'https' : 'http') +
      '://ajax.googleapis.com/ajax/libs/webfont/1/webfont.js';
    wf.type = 'text/javascript';
    wf.async = 'true';
    var s = document.getElementsByTagName('script')[0];
    s.parentNode.insertBefore(wf, s);
  })(); </script>

    <script type="text/javascript">

      function randomBackground () {

        var randomPicture = [Math.floor(Math.random() * 4)+ '.jpg'];
        return randomPicture;

      }


    </script>


    <title>NaturallyPizza</title>

    <!-- Bootstrap -->
    <link href="css/bootstrap.min.css" rel="stylesheet">

    <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
    <!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
    <!--[if lt IE 9]>
      <script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
      <script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
    <![endif]-->

    <link href='https://fonts.googleapis.com/css?family=Tenor+Sans|Rock+Salt' rel='stylesheet' type='text/css'/>


    <style>

    .navbar-collapse{
      color: white;
    }

    .navbar-brand {
        font-size: 1.5em;
        font-family: 'Rock Salt', sans-serif;
        color: white;
    }

    .navbar-default {
      margin-top: 30px;
      background-color: transparent;
      border: hidden;
      font-family: 'Tenor Sans', sans-serif;

      }


      .listing  a{
        font-size: 1.5em;
        color: white;
      }


      #topContainer {
        background-image: url("images/background/"+randomPicture);
        height: 500px;
        width: 100%;
        opacity: 0.95;
        background-size: cover;
        color: white;
    }

    .navbar-default .navbar-brand {
        color: white;
      }

 @media (max-width: 760px) {
    .navbar-default {
        background-color: lightgrey;
        opacity: 0.95;
      }
    }

    #topRow {

    margin-top: 130px;
    font-family: 'Tenor Sans', sans-serif;

    }

    .center {
      text-align: center;
    }

    .title {
      font-size: 3em;
      color: white;
    }
    .backing {

      background-color: grey;
      opacity: 0.6;
      border-radius: 10px;
    }

    .marginTop {

      margin-top: 30px;

    }

    .jumbotron {

      background-image: url("images/background/1.jpg");
      background-size: cover;
    }

  </style>



  </head>
  <body>

    <script type="text/javascript">alert(randomBackground);</script>

       <div class="navbar navbar-default navbar-fixed-top">

        <div class="container">

            <div class="navbar-header">
                <button class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
                    <span class="icon-bar color-me"></span>
                    <span class="icon-bar"></span>
                    <span class="icon-bar"></span>  
                </button>

                <a class="navbar-brand">NaturallyPizza</a>

            </div> <!-- class="navbar-header" -->

            <div class="collapse navbar-collapse navbar-right listing">
                <ul class="nav navbar-nav">

                    <li class="color-me"><a href="#home">Home</a></li>
                    <li><a href="#about">About</a></li>
                    <li><a href="#contact">Contact</a></li>

                </ul>

            </div> <!-- class="collapse navbar-collapse" -->

        </div>

    </div> <!--  class="navbar navbar-default" -->


   <div class="container-fluid contentContainer" id="topContainer">

        <div class="row-fluid">

              <div class="col-md-8 col-md-offset-2 backing" id="topRow">

                <h1 class="title marginTop center">Learn to make great Pizza!</h1>

              </div>

        </div>




 </div>

    <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
    <!-- Include all compiled plugins (below), or include individual files as needed -->
    <script src="js/bootstrap.min.js"></script>

    <script>
        $(".contentContainer").css("min-height", $(window).height());        
    </script>

  </body>
</html>

Answer 1

Your return statement is outside of your function. 您的return语句不在函数范围内。

Just use this 只是用这个

function randomBackground() {
    var randomPicture = [Math.floor(Math.random() * 4) + '.jpg'];
    return randomPicture;
}

jsFiddle : https://jsfiddle.net/hbhz3x4L/ jsFiddle： https ://jsfiddle.net/hbhz3x4L/

Answer 2

You cannot use JS inside a CSS, you have to set the style directly with javascript (put this code at the end of the page, after #topContainer ): 您不能在CSS内使用JS，必须直接使用javascript设置样式（将此代码放在页面末尾的#topContainer之后）：

<script>
    var el = document.getElementById('topContainer');
    el.style.backgroundImage = 'url(images/background/' + Math.floor(Math.random() * 4) + '.jpg)';
</script>

带有Javascript和CSS的随机背景生成器

问题描述

2 个解决方案

解决方案1
2 2015-09-14 14:35:36

解决方案2
2 已采纳 2015-09-14 14:41:26

带有Javascript和CSS的随机背景生成器

问题描述

2 个解决方案

解决方案1 2 2015-09-14 14:35:36

解决方案2 2 已采纳 2015-09-14 14:41:26

解决方案1
2 2015-09-14 14:35:36

解决方案2
2 已采纳 2015-09-14 14:41:26