Eliminate flash of unstyled content

问题

How do I stop the flash of unstyled content (FOUC) on a web page?

回答1:

What I've done to avoid FOUC is:

Set the body section as: <body style="visibility: hidden;" onload="js_Load()">
Write a js_Load() JavaScript function: document.body.style.visibility='visible';

With this approach the body of my web page is kept hidden until the full page and CSS files are loaded. Once everything is loaded, the onload event turns the body visible. So, the web browser remains empty until a point when everything pops up on the screen.

It is a simple solution but so far it is working.

回答2:

The problem with using a css style to initially hide some page elements, and then using javascript to change the style back to visible after page load, is that people who don't have javascript enabled will never get to see those elements. So it's a solution which does not degrade gracefully.

A better way therefore, is to use javascript to both initially hide as well as redisplay those elements after page load. Using jQuery, we might be tempted to do something like this:

$(document).ready(function() {
    $('body').hide();
    $(window).on('load', function() {
        $('body').show();
    });
});

However, if your page is very big with a lot of elements, then this code won't be applied soon enough (the document body won't be ready soon enough) and you might still see a FOUC. However, there is one element that we CAN hide as soon as script is encountered in the head, even before the document is ready: the HTML tag. So we could do something like this:

<html>
  <head>
  <!-- Other stuff like title and meta tags go here -->
  <style type="text/css">
    .hidden {display:none;}
  </style>
  <script type="text/javascript" src="/scripts/jquery.js"></script>
  <script type="text/javascript">
    $('html').addClass('hidden');
    $(document).ready(function() {    // EDIT: From Adam Zerner's comment below: Rather use load: $(window).on('load', function () {...});
      $('html').show();  // EDIT: Can also use $('html').removeClass('hidden'); 
     });  
   </script>
   </head>
   <body>
   <!-- Body Content -->
   </body>
</html>

Note that the jQuery addClass() method is called *outside* of the .ready() (or better, .on('load')) method.

回答3:

A CSS-only solution:

<html>
  <head>
    <style>
      html {
        display: none;
      }
    </style>
    ...
  </head>
  <body>
    ...
    <link rel="stylesheet" href="app.css"> <!-- should set html { display: block; } -->
  </body>
</html>

As the browser parses through the HTML file:

The first thing it will do is hide <html>.
The last thing it will do is load the styles, and then display all the content with styling applied.

The advantage to this over a solution that uses JavaScript is that it will work for users even if they have JavaScript disabled.

Note: you are allowed to put <link> inside of <body>. I do see it as a downside though, because it violates common practice. It would be nice if there was a defer attribute for <link> like there is for <script>, because that would allow us to put it in the <head> and still accomplish our goal.

回答4:

A solution which doesn't depend on jQuery, which will work on all current browsers and do nothing on old browsers, include the following in your head tag:

<head>
    ...

    <style type="text/css">
        .fouc-fix { display:none; }
    </style>
    <script type="text/javascript">
        try {
            var elm=document.getElementsByTagName("html")[0];
            var old=elm.class || "";
            elm.class=old+" fouc-fix";
            document.addEventListener("DOMContentLoaded",function(event) {
                elm.class=old;
                });
            }
        catch(thr) {
            }
    </script>
</head>

Thanks to @justastudent, I tried just setting elm.style.display="none"; and it appears to work as desired, at least in current Firefox Quantum. So here is a more compact solution, being, so far, the simplest thing I've found that works.

<script type="text/javascript">
    var elm=document.getElementsByTagName("html")[0];
    elm.style.display="none";
    document.addEventListener("DOMContentLoaded",function(event) { elm.style.display="block"; });
</script>

回答5:

This is the one that has worked for me and does not require javascript and it works great for pages with many elements and lots of css:

First, add a dedicated <STYLE> setting for the <HTML> tag with visibility 'hidden' and opacity as '0' at the top of your HTML, e.g, in the beginning of the <HEAD> element, for example, at the top of your HTML add:

<!doctype html>
<html>
<head>
    <style>html{visibility: hidden;opacity:0;}</style>

Then, at the end of your last .css stylesheet file, set the visibility and opacity styles to 'visible' and '1', respectively:

html {
    visibility: visible;
    opacity: 1;
}

If you already have an existing style block for the 'html' tag, then move the entire 'html' style to the end of the last .css file and add the 'visibility' and 'opacity' tags as described above.

https://gist.github.com/electrotype/7960ddcc44bc4aea07a35603d1c41cb0

回答6:

An other quick fix which also works in Firefox Quantum is an empty <script> tag in the <head>. This however, penalizes your pagespeed insights and overall load time.

I had 100% success with it. I think it's also the main reason, why above solutions with other JS in the works.

<script type="text/javascript">

</script>

回答7:

No one has talked about CSS @import

That was the problem for me i was loading two extra style sheets directly in my css file with @import

Simple solution: Replace all @import links with <link />

回答8:

I came up with a way that requires no real code change whatsoever, woohoo! My issue was related to importing several css files AFTER some javascript files.

To resolve the issue I just moved my CSS links so that they would be above my javascript imports. This allowed all my CSS to be imported and ready to go ASAP, so that when the HTML appears on the screen, even if the JS isn't ready, the page will be properly formatted

回答9:

Here is my code .. hope it solve your problem

set <body style="opacity:0;">

<script>
    $(document).ready(function() {
        $("body").css('opacity', 1);
    });
</script>

回答10:

The best solution I found till now is like this:

Add all styles of your header to a <style/> tag in <head/>
at the top of style tag add .not-visible-first{visibility: hidden} + other header style
Add css via JS at the end of body

document.getElementsByTagName("head")[0].insertAdjacentHTML("beforeend","<link rel=\"stylesheet\" href=\"/css/main.min.css?v=1.2.4338\" />");
And remember to add .not-visible-first{visibility: visible} to the end of main.min.css

This option will create better user experience

回答11:

You could try this with vanilla

function js_method(){
//todos
var elementDiv = document.getElementById("main");
elementDiv.style.display ="block";
}

<body onload="js_method()" id="main" style="display:none">
//todos
<h2>Hello</h2>
</body>

来源：https://stackoverflow.com/questions/3221561/eliminate-flash-of-unstyled-content

标签

css

fouc