I have an AngularJS document where I need to set fields in various parts of the document. This includes e.x. the <title> tag. So my document Looks like the following:
<html ng-app="test" ng-controller="TestCtrl">
<head>
<title>{{test1}}</title>
</head>
<body>
<h1>{{test1}}</h1>
...
</body>
</html>
As you can see I put the ng-controller in the <html> tag because I need to use the same scope across <head> and <body>. I could also set the controller on the individual elements but since I'm doing some POST and GET queries I think it's not a good idea because then they are performed multiple times.
Is using the ng-controller tag in the <html> element a good idea (is there a negative impact)? Are there better solutions?
Related
I was working with the following tutorial of D3.js: https://www.tutorialspoint.com/d3js/index.htm.
My issue is as follows:
I'm aware of that the location inside the HTML is at the end of the . I mean, I usually put it here:
<body>
<!-- HTML code -->
<script>
<!-- JS code or external JS link -->
</script>
</body>
With this practice, what I'm looking is to run JS after the HTML content renders.
But! When I follow this practice using D3.js, what I discover is that D3.js renders what I add (using d3("html").append(something to append), after the script tags.
For example!
<!DOCTYPE html>
<head>
<title>D3.js Test</title>
</head>
<body>
<div class="div_test">
<h1>I want the D3.js content after this div (but not inside the div)</h1>
</div>
<script type = "text/javascript" src = "https://d3js.org/d3.v4.min.js"></script>
<script>
d3.select("html").append("p").text("I get this text after the script tags");
</script>
</body>
</html>
I'm getting the content as follows:
<!DOCTYPE html>
<html>
<head>
<title>D3.js Test</title>
</head>
<body>
<div class="div_test">
<h1>I want the D3.js content after this div (but not inside the div)</h1>
</div>
<script type="text/javascript" src="https://d3js.org/d3.v4.min.js"></script>
<script>
d3.select("html").append("p").text("I get this text after the script tags");
</script>`
</body><p>I get this text after the script tags</p></html>
Questions!
Is the position of the tag correct?
Is there a possibility to keep the flow without adding a to anchor the expected new tag?
Thanks!!!
You can use selection.insert() to insert an element instead of appending it to the DOM. The second argument to that method determines where the newly created element is put into the DOM tree. If you just want to put it in front of the first <script> element you can do something like:
d3.select("body").insert("p", "script") // <-- insert before first <script>
If you need to place it after the <div>, no matter what the next element might look like, you can use the adjacent sibling combinator to select the sibling element directly following the <div> like so:
d3.select("body").insert("p", "div + *") // <-- insert before next element following div
<!DOCTYPE html>
<html lang="en">
<head>
<title>JavaScript Example</title>
<script>
function displayString() {
return "<h1>Main Heading</h1>"
}
displayString();
document.write("Execute during page load from the head<br>");
</script>
</head>
<body>
<script>
document.write("Execute during page load from the body<br>");
</script>
</body>
</html>
So this is my problem. No matter where I put the displayString(), the h1 just never seems to show up on the browser. Can anybody please help me see where I am wrong? I am new to JavaScript. Oh, and what I am trying to do is to call the function.
You need to write the returned String to the document:
<!DOCTYPE html>
<html lang="en">
<head>
<title>JavaScript Example</title>
<script>
function displayString() {
return "<h1>Main Heading</h1>"
}
document.write(displayString());
document.write("Execute during page load from the head<br>");
</script>
</head>
<body>
<script>
document.write("Execute during page load from the body<br>");
</script>
</body>
</html>
No matter where I put the displayString(), the h1 just never seems to
show up on the browser.
If you wish to add a new element to a document, several approaches are available:
document.write (effectively deprecated)
.innerHTML (sometimes useful, but can be slow)
DOM API - recommended approach
The recommended approach is to use the DOM API.
DOM stands for Document Object Model. Essentially it's the markup of your document represented as a tree-like structure of nodes. There are many DOM API functions which allow you to:
add
remove
append
prepend
insert
update
new DOM nodes.
Any DOM node may be added, removed or updated, including:
parent elements
child elements
sibling elements
element attributes
ids, classNames, classLists
custom data-* attributes
text nodes
Here is an example:
function displayMainHeading () {
let mainHeading = document.createElement('h1');
mainHeading.textContent = 'Main Heading';
document.body.prepend(mainHeading);
}
displayMainHeading();
<p>Paragraph 1</p>
<p>Paragraph 2</p>
Further Reading
This is a good primer to get you started:
A Beginners Guide To DOM Manipulation by Iqra Masroor
Is it possible to create your own text contents (text between the HTML tags) of my custom HTML tags?
I used this code:
<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-2.1.4.js"></script>
<script>
$(document).ready(function () {
$("eg").replaceWith("<h2>Put the text content of eg here</h2>");
});
</script>
</head>
<body>
<eg>My text</eg>
</body>
</html>
Between the <h2> tags (don’t think I should only use <h2> tags without JS) in my JavaScript code, any text can be placed that I like to have.
Example: <eg>I can type any text here but it’ll be still in h2 tag settings</eg>.
What should I write between <eg></eg> in JS to have any <h2> text content that will be written in my HTML code?
If you want to replace the <eg>Test</eg> with <h2>Test</h2> then you can just do this: $("eg").replaceWith("<h2>" + $("eg").html() + "</h2>");.
Here is an example: http://plnkr.co/edit/urd69pJSXQngGIsYYSjq
If I'm understanding correctly, you just want to append an element to the DOM, so you can just use the html method as follows:
$("eg").html("<h2>Any text can be placed here</h2>");
Have a look at the docs if you need more info.
Note: You closed but didn't open your body tag.
Replace:
</body>
With something like:
<body> <eg> Your custom content is between body tags now </eg> </body>
And you also have two HTML tags, remove the second
<html>
No. It wouldn't be HTML anymore.
However, if you wrote xHTML (which is a form of XML), then you could extend the DOM with your own elements. But that would be XML, not HTML.
And if you tried adding custom elements to a page, browsers wouldn't know what to do with them. Even if some browsers might display them, it's a very bad idea. Use a class name instead.
Creating and using custom tags is a bad idea. It should be avoided.
You are probably looking for this:
<!DOCTYPE html>
<html>
<head>
<script src="https://code.jquery.com/jquery-2.1.4.js"></script>
<script>
$(document).ready(function () {
$("#my_h2").html("<h2>Any text can be placed here</h2>");
});
</script>
</head>
<h2 id="my_h2"></h2>
</body>
</html>
For more, read-up on CSS selectors. (They are the same as jQuery selectors.)
Hope this helps.
I’ve got an HTML fragment like <p>Hello, World!</p> and want to attach it to the container HTML page that includes
<script src="lib/kotlin.js"></script>
<script src="my-app.js"></script>
There are two package that came to my mind:
kotlin.js.dom.html.window.document.*
kotlin.browser.document.*
Which should I use and how do I access the document’s root? I’ve already tried document.getElementById("container") whereby container is the id of a DIV. But this returns null. I also tried document.appendChild(node)...
Also which of the above packages should I prefer?
I just figured out that the JS output of the compiled app needs to be below the element that is referenced inside the app.
I’ve created a demo case that illustrates this:
<!DOCTYPE html>
<meta charset="utf-8"/>
<script src="lib/kotlin.js"></script>
<p>Look inside the JavaScript Console of your browser…</p>
<div id="container"></div>
<script>
console.log("Native JavaScript");
</script>
<!-- This script tag was misplaced. It needs to be placed after all elements you want to access in your DOM -->
<script src="kotlin-javascript-hello-world.js"></script>
I read that you should define your JavaScript functions in the <head> tag, but how does the location of the <script> (whether in the <head>, <body>, or any other tag) affect a JavaScript function.
Specifically, how does it affect the scope of the function and where you can call it from?
Telling people to add <SCRIPT> only in the head sounds like a reasonable thing to do, but as others have said there are many reasons why this isn't recommended or even practical - mainly speed and the way that HTML pages are generated dynamically.
This is what the HTML 4 spec says :
The SCRIPT element places a script
within a document. This element may
appear any number of times in the HEAD
or BODY of an HTML document.
And some sample HTML. Doesn't it look pretty all formatted here :)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<HTML>
<HEAD>
<TITLE>A document with SCRIPT</TITLE>
<META http-equiv="Content-Script-Type" content="text/tcl">
<SCRIPT type="text/vbscript" src="http://someplace.com/progs/vbcalc">
</SCRIPT>
</HEAD>
<BODY>
<SCRIPT type="text/javascript">
...some JavaScript...
</SCRIPT>
</BODY>
</HTML>
And something to look forward to in HTML 5 :
New async attribute in <SCRIPT> :
Note: There are ways [sic] a script can be
executed:
The async attribute is "true": The
script will be executed asynchrously
with the rest of the page, so the
script will be executed while the page
continues the parsing.
The async attribute is "false", but
the defer attribute is "true": The
script will be executed when the page
is finished with the parsing.
The normal rules of play still stand; don't use stuff before it's defined. :)
Also, take note that the 'put everything at the bottom' advice isn't the only rule in the book - in some cases it may not be feasible and in other cases it may make more sense to put the script elsewhere.
The main reason for putting a script at the bottom of a document is for performance, scripts, unlike other HTTP requests, do not load in parallel, meaning they'll slow down the loading of the rest of your page. Another reason for putting scripts at the bottom is so you don't have to use any 'DOM ready' functions. Since the script tag is below all elements the DOM will be ready for manipulation!
EDIT: Read this: http://developer.yahoo.com/performance/rules.html#js_bottom
One of the aspects of placement is performance. See this fine article within the YSlow discussion for why it's sometimes recommended you put them at the bottom of the document.
As for issues of scope, the usual visibility rules for Javascript (vars defined inside or outside of functions, local, global, closures, etc.) are not affected so far as I know.
Position of script tag does matter.
If you bind a Function with document Element then the document element has to be loaded first before we implement function. suppose getTeachers() is function in getTeachers.js file.
This will give you an error:
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Unit Teachers</title>
<head>
<script type="text/javascript" src="getTeachers.js"></script>
<script type="text/javascript">
document.getElementById("buttonId").onclick=function(){getResults()};
</script>
</head>
<body>
<form>
<input type = "button" id="buttonId" value = "Press for Results" /><br />
</form>
<span id="results" /></span>
</body>
</html>
It gives error before head is loaded first and it cannot find element with id specified.
The below code is correction:
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Unit Teachers</title>
<head>
<script type="text/javascript" src="getTeachers.js"></script>
</head>
<body>
<form>
<input type = "button" id="buttonId" value = "Press for Results" /><br />
</form>
<script type="text/javascript">
document.getElementById("buttonId").onclick=function(){getResults()};
</script>
<span id="results" /></span>
</body>
</html>
If your script refers to an ID on the page and the page has not been rendered (i.e. script is before HTML, or your script is executed with onload, rather then the DOM is ready) you can also get an error.
It doesn't. Most programming framework scatter scripts all throughout the page. I've only rarely seen problems because of that (and only from older browsers).
If you pull Javascripts in through XMLHttpRequest, like Diodeus said, it probably won't work. In my case, there was no error, the browser just ignores the new script(s).
I ended up using this, not terribly elegant but works for me so far:
http://zeta-puppis.com/2006/03/07/javascript-script-execution-in-innerhtml-the-revenge/
How to use execJS: http://zeta-puppis.com/2006/02/23/javascript-script-execution-in-innerhtml/
Note: Watch out for < in this line: for(var i=0;i<st.length; i++)
If you have an inline script (outside functions) located before functions it may call, you may get an error because they may not be not available yet. Not saying it is always going to happen, just that it may depending on browser type or version.
Javascript's scoping rules are similar to perl - you can call any function at the current or any higher scope level. The only restriction is that the function has to be defined at the time you call it. The position in the source is irrelevant - only the position in time matters.
You should avoid putting scripts in the <head> if possible as it slows down page display (see the link Alan posted).