I am new to Javascript. I am facing a problem with global variables. I can't figure out that why the global variables are not working as the code looks ok. Please Help me solve this problem.
I will breifly explain the code first.I have some text on a page which changes to text field when clicked. When I define the variables inside the functions body the code starts working fine. When these variables are defined globally as in the following code, the console displays this error: the variable is not defined. Here my code:
<!DOCTYPE HTML>
<html>
<head>
<title>Span to Text Box - Demo - DOM</title>
<script type="text/javascript" language="javascript">
var textNode = document.getElementById('text');
var textValue = textNode.firstChild.nodeValue;
var textboxNode = document.getElementById('textbox');
var doneButton = document.getElementById('done');
function change()
{
textboxNode.setAttribute('value', textValue);
textNode.style.display = 'none';
textboxNode.setAttribute('type','text');
doneButton.setAttribute('type','button');
}
function changeBack()
{
textNode.firstChild.nodeValue = textboxNode.value;
textNode.style.display = 'block';
textboxNode.setAttribute('type', 'hidden');
doneButton.setAttribute('type','hidden');
}
</script>
</head>
<body>
<p id="text" onClick="change()">Click me!</p>
<form onSubmit="return false;">
<input type="hidden" id="textbox" />
<input type="hidden" id="done" onClick="changeBack()" value="Done" />
</form>
</body>
</html>
Please Help!
Thanks in Advance.
As Adam said, the issue is that you are running javascript on the document before the document has been loaded. There are a number of ways to fix this, but the simplest is to just move your javascript code to the end of the body so the document has already been parsed and is ready before your code runs like this:
<!DOCTYPE HTML>
<html>
<head>
<title>Span to Text Box - Demo - DOM</title>
</head>
<body>
<p id="text" onClick="change()">Click me!</p>
<form onSubmit="return false;">
<input type="hidden" id="textbox" />
<input type="hidden" id="done" onClick="changeBack()" value="Done" />
</form>
<script type="text/javascript" language="javascript">
var textNode = document.getElementById('text');
var textValue = textNode.firstChild.nodeValue;
var textboxNode = document.getElementById('textbox');
var doneButton = document.getElementById('done');
function change()
{
textboxNode.setAttribute('value', textValue);
textNode.style.display = 'none';
textboxNode.setAttribute('type','text');
doneButton.setAttribute('type','button');
}
function changeBack()
{
textNode.firstChild.nodeValue = textboxNode.value;
textNode.style.display = 'block';
textboxNode.setAttribute('type', 'hidden');
doneButton.setAttribute('type','hidden');
}
</script>
</body>
</html>
The error is likely caused by grabbing DOM nodes before they're ready:
var textNode = document.getElementById('text');
This is likely returning either null or undefined since that DOM element hasn't been created yet.
Putting this script at the end of your body should solve your problem.
Or, if you'd like to use jQuery, you can do all this in
$(document).ready(function() {
var textNode = document.getElementById('text');
}
Related
I'm trying to change the text in an h2 element with the simplest code but don't get what I'm doing wrong :
html
<h2 id="tries">Number of tries : 0</h2>
javascript
document.getElementById("tries").innerHTML = 'new text';
There is nothing wrong wiht that. You asked JS to replace the innerHTML, and JS done that.
If you want to change only the value after the ":" then here is an example where I placed a span into the the p and I change the innerHTML of this span.
function changeText(value) {
//this is the point
document.getElementById("tries-value").innerHTML = value;
}
const input = document.querySelector("input");
input.addEventListener("change", (e) => changeText(e.target.value));
changeText(input.value)
<h2 id="tries">Number of tries : <span id="tries-value">0</span></h2>
<label for="input-number">Change the input:</label>
<input id="input-number" value="10" type="number" />
I just guess you did that and as you can see, it will fail
<!doctype html>
<html>
<head>
<script>
document.getElementById("tries").innerHTML = 'new text';
</script>
</head>
<body>
<h2 id="tries">Number of tries : 0</h2>
</body>
</html>
You can first do DOM Operations if the DOM is actually loaded, so you just listen to the window.load event and it will work
<!doctype html>
<html>
<head>
<script>
window.addEventListener('load', function () {
document.getElementById("tries").innerHTML = 'new text';
});
</script>
</head>
<body>
<h2 id="tries">Number of tries : 0</h2>
</body>
</html>
I was working on variables and loop frames and stumbled across this problem. I tried switching some things around but none have succeeded. I put the code in a validator and it showed the document as valid.
Whats missing?
Here's the code:
<!DOCTYPE html>
<html>
<head>
<title>JavaScript Example</title>
<script type="text/javascript">
function substitute() {
var myValue = document.getElementById('myTextBox').value
if (myValue.length == 0) {
alert('Please enter a real value in the text box!');
return;
}
var myTitle = document.getElementById('title');
myTitle.innerHTML = myValue;
}
</script>
</head>
<body>
<h1 id="title">JavaScript Example</h1>
<input type="text" id="myTextBox" />
<input type="submit" value="Click Me" onclick="substitute" />
</body>
</html>
Mentioning the name of a variable holding a function doesn't call the function. You have to actually call it explicitly.
This is usually done by placing () after the reference to the function.
onclick="substitute()"
This question already has answers here:
Why does jQuery or a DOM method such as getElementById not find the element?
(6 answers)
Closed 8 years ago.
Why does refButton get null in the following JavaScript code?
<html>
<head>
<title></title>
<script type="text/javascript">
var refButton = document.getElementById("btnButton");
refButton.onclick = function() {
alert('I am clicked!');
};
</script>
</head>
<body>
<form id="form1">
<div>
<input id="btnButton" type="button" value="Click me"/>
</div>
</form>
</body>
</html>
At the point you are calling your function, the rest of the page has not rendered and so the element is not in existence at that point. Try calling your function on window.onload maybe. Something like this:
<html>
<head>
<title></title>
<script type="text/javascript">
window.onload = function(){
var refButton = document.getElementById("btnButton");
refButton.onclick = function() {
alert('I am clicked!');
}
};
</script>
</head>
<body>
<form id="form1">
<div>
<input id="btnButton" type="button" value="Click me"/>
</div>
</form>
</body>
</html>
You need to put the JavaScript at the end of the body tag.
It doesn't find it because it's not in the DOM yet!
You can also wrap it in the onload event handler like this:
window.onload = function() {
var refButton = document.getElementById( 'btnButton' );
refButton.onclick = function() {
alert( 'I am clicked!' );
}
}
Because when the script executes the browser has not yet parsed the <body>, so it does not know that there is an element with the specified id.
Try this instead:
<html>
<head>
<title></title>
<script type="text/javascript">
window.onload = (function () {
var refButton = document.getElementById("btnButton");
refButton.onclick = function() {
alert('Dhoor shala!');
};
});
</script>
</head>
<body>
<form id="form1">
<div>
<input id="btnButton" type="button" value="Click me"/>
</div>
</form>
</body>
</html>
Note that you may as well use addEventListener instead of window.onload = ... to make that function only execute after the whole document has been parsed.
It always seems to be a problem and I fail to see why, I'm trying to change element p text by using his ID, element p id="para1" is inside PostEditor.html:
The elementID I want to change is para1 in the following html:
<!DOCTYPE html>
<html>
<head>
<title>Editor</title>
<link href="styles/editor.css" rel="stylesheet" type="text/css" media="screen" />
<script src="scripts/mainScript.js"> </script>
</head>
<body>
<!-- Input fields -->
<div class="center">
<form id=caller method="post">
<p id="para1" class="text"><Strong>Post your message</Strong></p>
<textarea id="textEditor" rows="16" cols="34" name="content"></textarea>
<input type="submit" onclick="urlLoader('caller','posthandler.php')" value="Post">
</form>
</div>
<!-- end Input fields -->
</body>
</html>
The following function is issued by a click on a link inside index.html and displaying the page you are seeing above and is then supposed to change its content:
From index.html I issue the function from link:
<a onclick="postEditing()"> Edit</a>
This line issue the following function:
function postEditing()
{
var result = window.open('PostEditor.html', 'newwindow', 'width=350,' + 'height=350');
result.document.getElementById("para1").innerHTML = "11111111111";
result.document.getElementById("para1").innerText = "11111111111";
result.document.getElementById("para1").value = "11111111111";
}
As you can see I tried three methods. I'd never understand what is the difference between them, but I tried all three and none worked!
It's because you're searching the document of the window which shows the index.html, not the document of the newly opened window. try following:
...
var editorWindow = window.open('PostEditor.html', 'newwindow', 'width=350,' + 'height=350');
editorWindow.document.getElementById("para1").innerHTML = "11111111111";
...
EDIT:
NOW i see the problem: in the function you're trying to access a property of the parameter element, but you don't pass a value for it. So this will end in an error because the accessed object is undefinded!
So you have three options to get it working:
test the parameter (always a good idea): var ID = null; if(element) ID = element.id;
pass a value: <a onclick="postEditing(this)"> Edit</a>
remove the line var ID = element.id;
SOLUTION: (TESTED)
I could not really say why, but the index.html found the para1 and can successfully set the new text. But somehow the new window will reinitialize the old value again.
So you have to do the changing in an handler you run at onLoad:
index.html:
<html>
<head>
<script>
function postEditing() {
var result = window.open('PostEditor.html', 'newwindow', 'width=350,' + 'height=350');
result.onload = function() {
result.document.getElementById("para1").innerHTML = "11111111111";
}
}
</script>
</head>
<body>
<a onclick="postEditing()"> Edit</a>
</body>
</html>
PostEditor.html:
<!DOCTYPE html>
<html>
<head>
<title>Editor</title>
<link href="styles/editor.css" rel="stylesheet" type="text/css" media="screen" />
<script src="scripts/mainScript.js"> </script>
</head>
<body>
<!-- Input fields -->
<div class="center">
<form id=caller method="post">
<p id="para1" class="text"><Strong>Post your message</Strong></p>
<textarea id="textEditor" rows="16" cols="34" name="content"></textarea>
<input type="submit" onclick="urlLoader('caller','posthandler.php')" value="Post">
</form>
</div>
<!-- end Input fields -->
</body>
</html>
I'm fairly sure you will need to query the return result of calling window.open like this:
function postEditing(element)
{
var ID = element.id;
var result = window.open('PostEditor.html', 'newwindow', 'width=350,' + 'height=350');
result.getElementById("para1").innerHTML = "11111111111";
result.getElementById("para1").innerText = "11111111111";
result.getElementById("para1").value = "11111111111";
}
[Untested though]
Your button type is submit, which is posting the form. The object is changing in the DOM, only after the script runs, the DOM is reloaded back to it's original state. Try changing your button type to "button", and you should see the P element change appropriately.
Edit: Here's the HTML I used to determine the above. Keeping the button as "submit" caused me to see the text change and then swap back. The HTML below should keep the text in place. HTH!
<!DOCTYPE html>
<html>
<head>
<title>Editor</title>
<script>
function postEditing(element)
{
document.getElementById('para1').innerHTML = "asdafs";
}
</script>
</head>
<body>
<!-- Input fields -->
<div class="center">
<form id=caller method="post">
<p id="para1" class="text"><Strong>Post your message</Strong></p>
<textarea id="textEditor" rows="16" cols="34" name="content"></textarea>
<input type="button" onclick="postEditing('caller')" value="Post">
</form>
</div>
<!-- end Input fields -->
</body>
</html>
I would like to make a button on a page that can call a JS function in the same page. The function will need to create (open) new window which its HTML code was given from the JS function itself. How can I do that?
The purpose of this is to produce a print friendly page out of a specific page.
Please notice: No AJAX can be used.
var opened = window.open("");
opened.document.write("<html><head><title>MyTitle</title></head><body>test</body></html>");
var w = window.open("");
w.document.writeln("<the html you wanted to write>")
function fu() {
var opened = window.open("");
opened.document.write("Your HTML here");
}
<textarea id="code" placeholder="Put code here!" width="500" height="500">
<DOCTYPE html>
<html>
<head>
</head>
<body>
</body>
</html></textarea>
<input id="width" placeholder="width">
<input id = "height" placeholder="height">
<button onClick="open();">Open the window!</button>
<button onClick="write();">Apply the html to the window</button>
<button onClick = "resize();">Resize the window!</button>
<script>
var win;
function open(){
win = window.open("", "", "");
win.resizeTo(screen.width, screen.height);
}
function resize(){
win.resizeTo(eval(document.getElementById("width")), eval(document.getElementById("height")))
}
function write(){
win.document.write(document.getElementByid("code").value);
}
</script>
Here you can input things and change the window. Hope you enjoy! :)