Order of javascript execution when loading html import - javascript

This http://webcomponents.org/polyfills/html-imports/ says following:
Under native imports, <script> tags in the main document block the loading of imports.
why then this:
<html>
<head>
<script>
console.log('index');
</script>
<script src="bower_components/webcomponentsjs/webcomponents-lite.js"></script>
<link rel="import" href="some-elt.html">
</head>
<body>
</body>
</html>
and some-elt.html:
<html>
<head>
<script>
console.log('import');
</script>
</head>
<html>
produces in chrome (native imports):
import
index
and in fireforx (polyfill):
index
import
?
It looks like <script> tags are blocked while imports are being loaded.
Is there also some way to ensure js execution before loading any imports?

I have created a quick pen here with markup you supplied.
It seems to be producing identical and correct output(index then import)for me in both FF and chrome.
But it is equally possible that you might be seeing something different in your console. Culprit here is not how the way script element is parsed,but rather console APIs. It is a non standard feature and might be returning different results for you as explained here
console.log is not standardized, so the behavior is rather undefined,
and can be changed easily from release to release of the developer
tools
To answer your question, script tag by design is blocking therefore any script which you put before your link rel="import" will be executed before browser encounters import tag.
Here is another pen(http://codepen.io/vishwaabhinav/pen/bEYwaK) to prove this(Also available below), where I am creating and appending divs to body in both imported and main document. It also works as expected i.e. index node is appended to body before import node.
<html>
<head>
<script>
var node = document.createElement('div');
node.innerHTML = 'Index';
document.body.appendChild(node);
</script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/webcomponentsjs/0.7.20/webcomponents-lite.js"></script>
<link rel="import" href="http://codepen.io/vishwaabhinav/pen/XXzjZW.html">
</head>
<body>
</body>
</html>

sorry everybody, it appears to be someting wrong with build scripts. The resulting html output is as following:
<!DOCTYPE html><html><head>
<!--<script src="https://cdnjs.cloudflare.com/ajax/libs/webcomponentsjs/0.7.20/webcomponents-lite.js"></script>-->
<link rel="import" href="some-elt.html">
</head>
<body>
<script src="index.js"></script></body></html>
https://github.com/PolymerElements/polymer-starter-kit/issues/669

Related

Is it possible to use javascript to modify a script element?

Is there a way to use javascript to modify a script element?
Like for example:
HTML:
<script id="something" src="/js/file.js"></script>
Javascript:
var something = document.getElementById("something");
something.src = "/js/anotherfile.js"
Is it possible? Because I have a bit of code that works like that and it sort of doesn't work
To be specific, here's the code:
<!DOCTYPE html>
<html>
<head>
<title>MyohTheGod's Website</title>
<link rel="icon" type="image/x-icon" href="/supercorn.gif" defer>
</link>
<link id="css" href="/css/dark.css" rel="stylesheet" type="text/css">
</link>
<script src="/js/particles.js" defer></script>
<script src="/js/header.js"></script>
<script src="/js/theme.js"></script>
<script>window.alert("Welcome to the Home of MyohTheGod. You can play games, check out our web proxies, and more. Also, please do check out the About page. Press OK to continue...");</script>
</head>
<body>
-snip-
</body>
<script id="foot" src="/js/footer.js"></script>
</html>
<script>
-snip-
</script>
var css = document.getElementById("css");
var foot = document.getElementById("foot");
function toggleDLmode(m) {
-snip-
if (dlmodebool) {
css.href = "/css/dark.css"
foot.src="/js/dark-footer.js"
} else {
css.href = "/css/index.css"
foot.src="/js/footer.js"
}
}
-snip-
It is working, do you inspect it? It does changed, but maybe you're thinking, "hm why this /js/anotherfile.js is not downloaded?". Well because of the script tag is already rendered and already downloaded, so you can't do that. What you can do though add NEW script tag.
Maybe this will help How to dynamically change the script src?. This links would explain more why your code "does not work".
There certainly is. You can use document.scripts which returns an collection that you can iterate through like an array. You can change the code using the innerHTML property very much like a normal element. See here https://developer.mozilla.org/en-US/docs/Web/API/HTMLCollection
Edited to add: If you've got a html page with multiple script tags, the document.script collection has each script in the order they appear. The code below will log out the source (src tag) or the actual javascript for each script element.
You can also 'write' javascript by setting the innerHTML property.
IMHO it's a bit of a solution that's looking for a problem but at least it gives you access to the number of scripts you have.
[...document.scripts].forEach(script => {
if (script.src != '') {
console.log("Script source:" + script.src);
} else {
console.log(script.innerHTML);
}
});

The server responded with a status of 404 (Not Found)

I am trying to instantiate a class in one JavaScript file in another HTML file but I keep on getting this error.
Here is the code for the JavaScript file:
class Puzzle {
constructor(fenStart, pgnEnd) {
this.fenStart = fenStart;
this.pgnEnd = pgnEnd;
}
}
And here is the code for the HTML. It should be noted that I am also using chessboard.js and chess.js and that everything is saved in the same folder.
<!DOCTYPE html>
<html>
<head>
<title>Chess</title>
<base href="http://chessboardjs.com/" />
<link rel="stylesheet" href="css/chessboard.css" />
</head>
<body>
<script src="js/chess.js"></script>
<div id="board" style="width: 400px"></div>
<p>PGN: <span id="pgn"></span></p>
<script src="js/json3.min.js"></script>
<script src="js/jquery-1.10.1.min.js"></script>
<script src="js/chessboard.js"></script>
<script src="class.js"></script>
<script>
var pgnEl = $('#pgn');
const x = new Puzzle("test", "test");
pgnEl.html(x.fenStart);
</script>
</body>
</html>
What is causing this error and how can I fix it?
This could be a result from improper file locations, like #sideroxylon said, js/class.js instead of class.js.
"The HTML <base> tag is used to specify a base URI, or URL, for relative links." https://www.tutorialspoint.com/html/html_base_tag.htm This could be another reason your file is inaccessible.
It could also be from certain URL's being blocked. Try opening Developer Console (CTRL-SHIFT-I or F12) and looking for any errors on your page.
If you're loading over HTTPS any content from an HTTP source may be blocked. Here is your exact code (using online versions of each library) but with the class.js file loaded in as a regular script tag and including the starting <body> tag.
https://jsfiddle.net/ckazwozg/ As you should see, it is working quite well.
Edit: For convenience, here is the raw source code from the JSFiddle.
<!DOCTYPE html>
<html>
<head>
<title>Chess</title>
<link rel="stylesheet" href="https://rawgit.com/oakmac/chessboardjs/master/src/chessboard.css" />
</head>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/chess.js/0.10.2/chess.js"></script>
<div id="board" style="width: 400px"></div>
<p>PGN: <span id="pgn"></span></p>
<script src="https://cdnjs.cloudflare.com/ajax/libs/json3/3.3.2/json3.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<script src="https://rawgit.com/oakmac/chessboardjs/master/src/chessboard.js"></script>
<script>
// class.js
class Puzzle {
constructor(fenStart, pgnEnd) {
this.fenStart = fenStart;
this.pgnEnd = pgnEnd;
}
}
</script>
<script>
var pgnEl = $('#pgn');
const x = new Puzzle("test", "test");
pgnEl.html(x.fenStart);
</script>
</body>
</html>
I had the same error however what I did was ensure all my files are been saved to the root folder in your case I think that's js(since all your extension points to that location) in my case I've used only the file name after giving it javascript extension (.js) e.g...

Code text appears instead of executing

I need some helping loading my JavaScript game on Chrome.
I wanted to code the traditional Snake game in JavaScript using a framework called p5.js, and I started with the canvas. The problem happens when I open the JavaScript file in Chrome (which I linked in my index.html file with a script tag).
Instead of the grey canvas appearing, per my JavaScript code, the code itself shows up on the Chrome page. Here's my code, have a look:
HTML
Snake | JS
<body>
<script src="F:\Code\JS\p5\p5-zip\p5.js" type="text/javascript"></script>
<script src="F:\Code\JS\p5\p5-zip\addons\p5.dom.js" type="text/javascript"></script>
<script src="F:\Code\JS\p5\p5-zip\addons\p5.sound.js" type="text/javascript"></script>
<script src="F:\Code\JS\Snake\sketch.js" type="text/javascript"></script>
</body>
</html>
And here's the JS:
function setup() {
createCanvas(800, 800);
}
function draw() {
background(51);
}
Specs:
Chrome, Windows 10 Anniversary Edition.
P.S. Javascript is enabled, I have checked.
Try these things
1) Test your js code on www.codepen.io/pen/, some javascript doesn't run properly when local. (F:\Code)
2) Try to put your script at the end of the body tag. Attention that the scripts are loaded in the order they appear. Consider the dependencies.
Assuming the path F:\Code\JS\p5\p5-zip\ to your files are correct and you are not working in a zipped folder.
You should have a file like index.html, wich will be the root of your website.
Here's a minimal example, including your scripts:
<!doctype html>
<html lang="fr">
<head>
<meta charset="utf-8">
<title>Titre de la page</title>
<link rel="stylesheet" href="style.css">
</head>
<body>
<script src = "F:\Code\JS\p5\p5-zip\p5.js" type="text/javascript"></script>
<script src = "F:\Code\JS\p5\p5-zip\addons\p5.dom.js" type="text/javascript"></script>
<script src = "F:\Code\JS\p5\p5-zip\addons\p5.sound.js" type="text/javascript"></script>
<script src = "F:\Code\JS\Snake\sketch.js" type = "text/javascript"></script>
</body>
</html>
Your javascript files should be placed in the bottom of the page,
just before the closing body tag
You must reference your js file in a good order for preventing some dependency issues
If you are able to browse your index.html file, right click on the page -> "show source code" and try to click on your js files reference, if the path is not correct you will have a 404 not found error.

Implement JS in HTML

It should be easy,
but as easy as it should be I can't solve the problem.
If I'm typing the following HTML and JS code into an online editor,
everything works fine but if I'm typing this into my (offline) editor it won't work.
Here's the online code:
http://jsbin.com/kenurunahu/1/edit?html,js,output)
I bet it has something to do with the loading order and how the files are linked.
Thats how my (lokal) HTML-file looks like (where the files are linked):
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" content="Index.css">
<script src="Script.js"></script>
</head>
<body>
<p id="demo">
something
</p>
</body>
</html>
Many Thanks for Help!
[Update]
Firefox and Chrome display the JS file. Sometimes I get an error message that says 'innerHTML is null', but if I write the same code into the console everything works fine.
you have the error when the js script is loaded before the html dom is fully loaded by the browser. A simple solution for your testing is to place the script include at the end of your html page, like this :
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" content="Index.css">
</head>
<body>
<p id="demo">
something
</p>
<script src="Script.js"></script>
</body>
</html>
A better solution is to run your script only when the dom is fully loaded. For example with the body onload event :
<body onload="yourFunc()">
Or event better by using only js code, for example with jquery ready function or by writing a simple custom handler that should work on all major browsers :
document.addEventListener("DOMContentLoaded", function(event) {
//call your func here
});
Hope that helps.
A few guesses:
Capitalization is important. If the file is named script.js do not link to Script.js
Is your js file in the same folder as the index.html document? Because that is what you are saying.
Normally, we arrange our file structure something like this:
public_html
- css
- js
- img
- inc
If your styles/scripts are stored in sub-folders, such as js and css, then you must amend your references to:
<link rel="stylesheet" content="css/Index.css">
<script src="js/Script.js"></script>
As a good practice, your scripts should be placed at the closing of body tag. External scripts are blocking and hence it would make sense we do not put them at the top. Also, when your script placed at the top runs, your DOM may not be ready, which means any element your script is trying to access may not be present in DOM at all which results in your error.
Hence, all your scripts should be at the closing of body tag. That way when the script loads and runs, you can be assured that the DOM is ready.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" content="Index.css">
</head>
<body>
<p id="demo">
something
</p>
<script src="Script.js"></script>
</body>
</html>

css not being applied to document.write text

I'm writing text to a page using document.write for a Chrome extension, but the associated custom CSS isn't applied:
<!DOCTYPE html>
<html>
<head>
<title>TITLE GOES HERE</title>
<link rel="stylesheet" href="css/popup.css" type="text/css" />
</head>
<body>
<script type="text/javascript">
...
function showFolder(folder) {
console.debug('FOLDER: '+folder.title);
document.write('<p>'+folder.title+'<br></p>');
}
</script>
</body>
</html>
The CSS is simple, just for debugging:
p {
color: red;
}
I can get it to work if I put the stylesheet link inside the function showFolder, but that can't be the proper way to do it. I'm learning jscript/CSS on the fly, so the answer is probably something remedial. Is the problem in the jscript, the CSS or both?
Use innerHTML.
<div id="towrite"></div>
then you can write in it like this:
div=document.getElementById('towrite');
div.innerHTML = '<p>'+folder.title+'<br></p>';
If you run your document.write() before the page finishes loading (perhaps calling your showFolder call directly from a script on the page), then the text will be written into the document as you might expect.
However, if you call document.write after the page loads, as in an event handler, you will be writing an entirely new page. This is usually not what you want.
Instead, follow Zoltan's advice and set the innerHTML property of an empty div.
I'm not javascript expert... I mainly use jQuery.. but try this, kind of makes sense:
<!DOCTYPE html>
TITLE GOES HERE
<script type="text/javascript">
...
function showFolder(folder) {
console.debug('FOLDER: '+folder.title);
document.write('<p>'+folder.title+'<br></p>');
}
</script>
<link rel="stylesheet" href="css/popup.css" type="text/css" />
EDIT:
So the above didn't work, but I just thought about another solution. When are you actually calling the function? Try to put it in <body onLoad="functionnamehere()">
No idea if that works, but give it a try.

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