From what I know, the browser can only request the assets (JS, CSS) after parsing the HTML. But analyzing the "Performance" tab on Edge's DevTools, the "Send Request" for the w3schools30.css stylesheet happens before the parsing is even started, as we can see indicated by the green arrow and other data in this image.
I'm using a simple example. Here's index.html:
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="https://www.w3schools.com/lib/w3schools30.css"/>
</head>
<body>
Performance testing
<script src="index.js"></script>
</body>
</html>
And the index.js:
setTimeout(() => {}, 1000)
Am I misunderstanding the timeline or there is a circunstance where this happens?
I think it is related with a feature called "preload scanner" on Chromium browsers. This article says:
A preload scanner's role is speculative, meaning that it examines raw
markup in order to find resources to opportunistically fetch before
the primary HTML parser would otherwise discover them.
Related
I have a page where the <title> tag contains some text (specifically: the department name) that screen readers do not pronounce very well (the department's name is ‘AskHR’ -- it’s the HR department’s helpdesk).
I want to provide screen readers with a more pronounceable version (‘Ask H R’) whilst keeping the more stylised version for visual display. I was thinking of using aria-label to achieve this, but I’m uncertain whether it can be applied to the <title> element in the <head>.
Can anyone confirm whether or not this is valid?
I don't think this is valid.
First not all screen readers are made equal!
What you're trying to do may work in some but not in others. For example VoiceOver reads out "AskHR" as you would expect. (And ignores the aria-label attribute.)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title aria-label="xxx">AskHR</title>
</head>
<body>
<button aria-label="close">X</button>
</body>
</html>
I think this is perhaps closer to what you're trying to do but support is limited:
.label {
speak-as: spell-out
}
See https://developer.mozilla.org/en-US/docs/Web/CSS/#counter-style/speak-as
If we inspect the example above in Chrome, you see this for the <button> element:
The aria-label attribute takes over the button content. VoiceOver reads out "close" instead of "x".
However this is what we see for <title>:
In a presentation, I would like to create a Twitter Timeline with a few selected tweets. In the best case it should look as natural as if someone went to Twitter on his own computer or saw it on his smartphone.
I am using LateX Beamer for the rest of the slides, but I am flexible if it is another software that allows to export a PDF/Image that I could include in LateX.
(There are a lot of tools on how to integrate live Tweets in PowerPoint / Keynote , but I want to do it for historical tweets and will be offline during the presentation.)
I was trying the following:
- Simply take screenshots of the tweet and arrange them within LateX or PowerPoint. Looks ok but not super nice, and quite cumbersome to do.
Since it is possible to extract an html of a tweet to embed on a homepage, I thought of doing this for the presentation. Unfortunately, I don't know much of html / reveal.js presentations.
Has anybody found a good solution for a similar problem?
EDIT:
I started reveal.js and found the following plugin: https://github.com/rajgoel/reveal.js-plugins/tree/master/embed-tweet
I was then trying to apply it and followed the intros to reveal.js and also saved the source code of the plugin into my plugin folder for reveal.js. However, it does not work (=Returning a blank page in the html). Can anybody point me to my error? (I am completely new to reveal.js / html so sorry if it is basic?)
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Reveal.js 3 Slide Demo</title>
<link rel="stylesheet" href="css/reveal.min.css">
<link rel="stylesheet" href="css/theme/default.css" id="theme">
<!--Add support for earlier versions of Internet Explorer -->
<!--[if lt IE 9]>
<script src="lib/js/html5shiv.js"></script>
<![endif]-->
</head>
<body>
<!-- Wrap the entire slide show in a div using the "reveal" class. -->
<div class="reveal">
<!-- Wrap all slides in a single "slides" class -->
<div class="slides">
<!-- ALL SLIDES GO HERE -->
<!-- Each section element contains an individual slide -->
<section>
<div class="tweet" data-src="https://twitter.com/marcfbellemare/status/972558957645631488"></div>
</section>
</div>
</div>
<script src="lib/js/head.min.js"></script>
<script src="js/reveal.min.js"></script>
<script>
// Required, even if empty.
Reveal.initialize({
// ...
dependencies: [
// ...
{ src: 'plugin/embed-tweet/embed-tweet.js' },
// ...
]
});
</script>
</body>
</html>
I created a minimal polymer-2-application using the cli tool. Without any changes, just running polymer serve, the initial load time for the first visit is 4s on Fast3G. It remains 4s also after polymer build.
On top are loading times for any html import for shell, polymer elements, firebase, ...
Do I just have to accept the load time of 4s+ and use a loader in index.html, server-side rendering & amp or some other workarounds or am I missing something?
I know that I can speed up the load of the second visit with service-worker but the first-time visitor will always have to be patient?
Here the code (no changes from polymer-cli)
index.html:
<!DOCTYPE html><html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, minimum-scale=1, initial-scale=1, user-scalable=yes">
<title>polymer_min.</title>
<meta name="description" content="testing minimal loading time for Polymer app">
<link rel="manifest" href="/manifest.json">
<script src="/bower_components/webcomponentsjs/webcomponents-loader.js"></script>
<link rel="import" href="/src/polymer_min-app/polymer_min-app.html
</head>
<body>
<polymer_min-app></polymer_min-app>
</body>
</html>
Polymer_min-app
<link rel="import" href="../../bower_components/polymer/polymer-element.html">
<dom-module id="polymer_min-app">
<template>
<style>
:host {
display: block;
}
</style>
<h2>Hello [[prop1]]!</h2>
</template>
<script>
class Polymer_minApp extends Polymer.Element {
static get is() { return 'polymer_min-app'; }
static get properties() {
return {
prop1: {
type: String,
value: 'polymer_min-app'
}
};
}
}
window.customElements.define(Polymer_minApp.is, Polymer_minApp);
</script>
</dom-module>
By default Polymer loads its dependencies arbitrarily as seperate files which results in couple of seconds load time - notice the "waterfall" in the network tab of your Dev Tools. For example, one of our tools makes 100+ requests at startup to load dependencies like elements.
Not using a service worker, server side rendering, client side caching, or alike will result in comparable load times on subsequential page loads.
Bundling your app will not effect that unless you load the index file from the build-directory. Dependencies (e.g. from bower_comonents) will be baked into your app elements in the src subfolder of your build, which leads to less requests with uglified code - which mean you send less bytes over the wire. Out tool mentioned above looses about 50% of its weight by bundling, making only 15 requests on load.
Sample image https://imgur.com/a/g9UPM
Independently of bundling you should at least take care of caching by configuring your server, or maybe use a service worker. When running NodeJS you might have a look at https://github.com/Polymer/prpl-server-node.
It says here that it is not within HTML4, though I don't really see where that's spelled out in the text.
From what I can tell, based on this, it is ok to do so in HTML5 but I'm not entirely sure (assuming style is an HTML element?)
I am using this to rotate out a stylesheet and want it to be as valid as possible according to HTML5 specs, so wondering if I should rewrite it with a data-* element.
+1 Interesting question!
Instead of using a style block, you should consider linking (link) to your stylesheets and then switch them out by referencing an id or a class.
That said, title is perfectly acceptable for a style tag in HTML5. You can use this as a hook for your stylesheet switching.
http://www.w3.org/TR/html5/semantics.html#the-style-element
Fyi... this validates
<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<style title="whatever"></style>
</head>
<body>
Test body
</body>
</html>
http://validator.w3.org/#validate_by_input+with_options
I've just put the following code into the W3C validator and it has no errors :)
<!DOCTYPE html>
<html>
<head>
<title>Title</title>
<style id="test"></style>
</head>
<body>
Test body
</body>
</html>
I think the W3C Validator is a good resource for this type of thing, it is marked as experimental but that's because the standard is yet to be be finalised.
It is not valid in HTML4 (as per the spec) and data-* attributes are not either. That is, the document will not validate against the Doctype spec if you use these attributes.
Regardless of whether the document validates or not, browsers will ignore elements that they do not recognize.
Style tags are DOM elements like any other tag, so you can add any attributes you want.
I have been reading up on this, and it seems that if you use ajax you can only bring in content that resides on the same domain whereas with an iframe you can bring in content from any domain. Is that the case? What other differences are there?
Bear in mind they're two completely separate technologies.
A (i)frame really loads a complete HTML page in area into the browser. Whether the page is on the same or another domain, for pure viewing, doesn't matter.
Ajax only describes a system to facilitate JavaScript to talk with (and with current security restriction across browser, only with) the server from which you document within which you generated the JavaScript call from.
The (i)frame technology loads and renders a complete HTML page from any URL given. Certain security restrictions accessing other documents from other domains with JavaScript still apply.
With Ajax, it's only meant to use purely JavaScript to talk to the originating server (send some data) and usually get some data back. In JavaScript. What this data is and what you do with it, is up to you. Whether you insert it into the DOM (Document Object Model), exchange parts or load a new page is up to you.
To a certain degree you have all freedom you want. You can have an (i)frame on a page, still make a Ajax call and decide to load another URL into the (i)frame. Or use the Ajax return value to generate new HTML dynamically inside the (i)frame. Or outside, in another document.
The security restrictions applying in this case is called "same origin policy".
Quite simply, an iframe is like a regular frame, but it doesn't split the browser window up into sections, it sits right inside a page and is affected by the scrollbar.
Ajax, on the other hand, uses javascript to do partial loads of a page, allowing small amounts of data to be loaded from the server without needing to do a complete postback. For example, Youtube uses Ajax when you post comments, vote, queue videos to play, etc. They do this so that your video isn't interrupted and restarted by a complete page postback.
Besides these differences mentioned by others, there are others as well.
iframe loads an entire html/php page, whether it is from the own server or other external server. Usually, it has a fresh <html>, <head> and <body> tag as well. Ajax only loads part of the html/php page.
Besides, Ajax pulls the CSS (and maybe, even javascript codes) from the parent file, but in case of Iframe, it cannot pull the same.
E.g this is the master file coding.
<!doctype html>
<html>
<head>
<style>
.gappu {background-color:black;color:red;}
</style>
<meta charset="utf-8">
<script src="../AllJqueries/jquery-1.11.3.min.js"></script> <!-- Use your own jQuery file -->
<script>
<!--
$(document).ready(function(){
$.ajax({url:"slave1.php?bare=true", success:function(data){
$(".myDomain").html(data);
}});
}); /* End of Main Jquery */
//-->
</script>
<title>Ajax vs Iframe</title>
</head>
<body>
<div class="myDomain"></div>
<div>Iframe below</div>
<iframe width="100%" height="500px" src="slave1.php"></iframe>
</body>
</html>
Now, we also have another file, named as slave1.php
<?php
if(isset($_GET['bare'])) $bare = $_GET['bare'];
else $bare = false;
if(!$bare):
?>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<style>
.gappu {background-color:blue;color:yellow;}
</style>
<!-- You can remove the above style later, and see the difference. The parent style will not apply for iframe -->
<title>Inside the Iframe</title>
</head>
<body>
<?php endif; ?>
<div class="gappu">Hi, welcome to this demo</div>
<?php if(!$bare): ?>
</body>
</html>
<?php endif;
In case of Ajax call, the line Hi, welcome to this demo will be in black background and red color, since it is borrowing the css from the parent. But in iframe, it will be in blue background and white color, which is defined in slave1.php. You can remove the style from slave1.php, and you will find plain text printed in iframe format.
Hope this helps. Cheers.
Vijay Srinivas