I have a question about javascript/html.
First, I have this:
var post = document.body.getElementsByClassName("post");
var x=post[i].getElementsByClassName("MyDiv")[0].innerHTML;
I get from the debugger that x is not defined, it doesn't exists.
This javascript function runs onload of the body. I am sure that I gave the right classnames in my javascript, so it should find my div.
So, I read somewhere that sometimes javascript does not find an element because it is not yet there, it is not yet created in the browser ( whatever that means).
Is it possible that my function can't find the div with that classname because of this reason?
Is there a solution?
So, I read somewhere that sometimes javascript does not find an element because it is not yet there, it is not yet created in the browser ( whatever that means).
Browsers create the DOM progressively as they get the markup. When a script element is encountered, all processing of the markup stops (except where defer and async have an effect) while the script is run. If the script attempts to access an element that hasn't been created yet (probably because its markup hasn't been processed yet) then it won't be found.
This javascript function runs onload of the body.
If that means you are using something like:
<body onload="someFn()"...>
or perhaps
<script>
window.onload = function() {
someFn();
...
}
</script>
then when the function is called, all DOM nodes are available. Some, like images, may not be fully loaded, but their elements have been created.
If it means you have the script in the body and aren't using the load event, you should move the script to the bottom of the page (e.g. just before the closing body tag) and see if that fixes the issue.
Okay, instead of calling functions with
body onload, use jQuery's ready() function, or, if you don't want to use jQuery, you can use pure javascript, but this is up to you:
// jQuery
$(document).ready(function() {
var post = document.getElementsByClassName("post"),
x = post[i].getElementsByClassName("MyDiv")[0].innerHTML;
});
// JavaScript
window.onload = function initialization() {
var post = document.getElementsByClassName("post"),
x = post[i].getElementsByClassName("MyDiv")[0].innerHTML;
}
A few side notes, I don't know what the use of innerHTML
is, and also if you're doing a for loop with i then definitely
post that code, that's kind of important.
After some discussion, my answer seems to have worked for you, but you can also place your script at the end of your body tag as #RobG has suggested.
Related
I am pretty new to JavaScript so I don't know the ins and outs of the language but I do have some knowledge of it. I created a self invoked function that would sort an array of zip-codes and then output it to a div element in the html file.
Unfortunately, the output isn't going into the div element because the function is executed before the html elements is ready, therefor it doesn't exist.
Is there anyway that I could access the div element within the function without having to use Window.Load, etc?
Thank you! click on the link below to view my function.
Screenshot of function
Is there anyway that I could access the div element within the
function without having to use Window.Load, etc?
Just move that code to the end of your html - after elements in question.
For example after </body>
From what I know, you can't access the DOM if it doesn't exist in that moment.
I know I know, don't use window.onload. But I assure you this is different than waiting for the DOM to load and then follow up with your calculations.
You can have a function evaluate something, then actually hang on the result and wait, and then finally fill the innerHTML when the DOMContentLoaded event has fired... or perhaps something of similar flavour, have a look at this.
<script>
const calculations = (function () {
// Super smart calculations...
var output = "Result of smart calculations";
function findWhereOutputGoes() {
return document.getElementById('output-div');
}
return {
output: output,
findWhereOutputGoes: findWhereOutputGoes,
}
})();
document.addEventListener('DOMContentLoaded', function(){ // Fires as soon as DOM has loaded
calculations.findWhereOutputGoes().innerHTML = calculations.output;
});
</script>
<div id="output-div">
</div>
I have this ajax call that's suppose to run when a key is pressed on a specific textbox. Once in the call, it runs a function that fires an alert. But, its doesn't work. Maybe it's cause I wrote the call using an old forum post as reference. Assume, I called the jquery library cause on my test I did but I didn't post it here.
This is what I've tried so far:
<script>
$("#<% =tb.ClientID%>").keydown
(
function ()
{
debugger; alert("hello");
}
);
</script>
<body>
<asp:TextBox Id = "tb" runat = "server"/>
</body>
I'm new to these kind of calls. I'm very familiar with js functions, but I've never done this. Any explanations and suggestions, would be greatly appreciated.
HTML is processed line by line. So when it processes the contents of that script tag, it hasn't yet processed anything further down, such as the body tag or its contents.
Inside the script, you're running $("#<% =tb.ClientID%>"). It'll try to find an element by its ID, but since the body hasn't been processed yet, it will yield no results. With no results, it has nothing on which to set the listener for .keydown.
It's in cases like these that using jQuery's $(document).ready function or its equivalents becomes incredibly important and crucial to the code. $(document).ready accepts a function, and it will wait until the DOM is fully loaded before executing that code. So putting $("#<% =tb.ClientID%>").keydown.... inside of a $(document).ready will ensure that the element has a chance to enter the DOM before the .keydown listener is attached to it.
You can find the docs for $(document).ready() here.
As soon as body DOM node is available, I'd like to add a class to it with JavaScript.
I want this to happen as soon as possible, before any of body's children are loaded.
Right now, I'm using an inline script right after opening body tag. Is there a less obtrusive way?
Might be a bit late to the party but...
You can just tap into the browser rendering cycle. Thus you don't have to deal with timeouts which leak memory (if improperly used).
var script = document.createElement('script');
script.src = '//localhost:4000/app.js';
(function appendScript() {
if (document.body) return document.body.appendChild(script);
window.requestAnimationFrame(appendScript);
})();
I would imagine this will differ between browsers.
One solution may be to test for it by placing a script immediately inside the opening <body> tag, then running your code at an interval to add the class.
<body>
<script>
function add_class() {
if(document.body)
document.body.className = 'some_class';
else
setTimeout(add_class, 10); // keep trying until body is available
}
add_class();
</script>
<!-- rest of your elements-->
</body>
jQuery does something similar internally to deal with a particular IE bug.
There isn't a guarantee that the descendant elements won't be loaded though, since again it will depend on when the particular implementation makes the body available.
Here's the source where jQuery takes a similar approach, testing for the existence of the body in its main jQuery.ready handler, and repeatedly invoking jQuery.ready via setTimeout if the body isn't available.
And here's an example to see if your browser can see the <body> element in a script at the top of the element, before the other elements. (Open your console)
Here's the same example without needing the console.
What is the best unobtrusive way of invoking something after the page is being loaded in plain JavaScript? Of course in jQuery I would use:
$(document).ready(function(){...});
but I am not sure about the most reliable approach in plain js.
Clearly
window.onload = ...
is not proper solution, because it would overwrite previous declaration.
What I am trying to do is to insert an iframe into a div after the page is loaded, but maybe there are actually better ways of doing it. My plan is to do something like:
window.onload = function(divId){
var div = document.getElementById(divId);
div.innerHTML = "<iframe src='someUrl' .. >";
}
EDIT:
Apologies for not including all necessary details.
The script is not for my website - the idea is to show a part of my site (a form) on external web sites. The priority is to minimize the effort someone has to put to use my code. That is why I would like to keep everything in js file and absolutely nothing in <script> - except of <script src="http://my.website/code.js" />. If I change URL of an iframe or I would like to add some features, I would like to update the code on all other web sites without asking them to make any changes.
My approach might be wrong - any suggestions are very welcome.
//For modern browsers:
document.addEventListener( "DOMContentLoaded", someFunction, false );
//For IE:
document.attachEvent( "onreadystatechange", someFunction);
`attachEvent` and `addEventListener` allow you to register more than one event listener for a particular target.
See:
https://developer.mozilla.org/en/DOM/element.addEventListener
Also definitly worth looking at how jQuery does it:
http://code.jquery.com/jquery-1.7.js Search for bindReady.
Use window.addEventListener and the events load or DOMContentLoaded:
window.addEventListener('DOMContentLoaded',function(){alert("first handler");});
window.addEventListener('DOMContentLoaded',function(){alert("second handler");});
object.addEventListener('event',callback) will insert an event listener into a queue for that specific object event. See https://developer.mozilla.org/en/DOM/element.addEventListener for further information.
For IE5-8 use window.attachEvent('event',callback), see http://msdn.microsoft.com/en-us/library/ms536343%28VS.85%29.aspx. You can build yourself a little helper function:
function addEventHandler(object,szEvent,cbCallback){
if(typeof(szEvent) !== 'string' || typeof(cbCallback) !== 'function')
return false;
if(!!object.addEventListener){ // for IE9+
return object.addEventListener(szEvent,cbCallback);
}
if(!!object.attachEvent){ // for IE <=8
return object.attachEvent(szEvent,cbCallback);
}
return false;
}
addEventHandler(window,'load',function(){alert("first handler");});
addEventHandler(window,'load',function(){alert("second handler");});
Note that DOMContentLoaded isn't defined in IE lesser 9. If you don't know your recipient's browser use the event load.
Just put your script include at the very end of the document, immediately before or after the ending </body> tag, e.g.:
(content)
(content)
<script src="http://my.website/code.js"></script>
</body>
</html>
All of the markup above the script will be accessible via the usual DOM methods (reference). Obviously, not all ancillary resources (images and such) will be fully loaded yet, but presumably that's why you want to avoid the window load event (it happens so late).
The only real purpose of ready-style events is if you don't control where the script gets included (e.g., libraries) or you need to have something execute prior to the page load and something else after the page load, and you want to avoid having two HTTP requests (e.g., for two different scripts, one before load and one after).
I am trying to load Skyscanner API dynamically but it doesn't seem to work. I tried every possible way I could think of and all it happens the content disappears.
I tried console.log which gives no results; I tried elements from chrome's developers tools and while all the content's css remains the same, still the content disappears (I thought it could be adding display:none on the html/body sort of). I tried all Google's asynch tricks, yet again blank page. I tried all js plugins for async loading with still the same results.
Skyscanner's API documentation is poor and while they offer a callback it doesn't work the way google's API's callback do.
Example: http://jsfiddle.net/7TWYC/
Example with loading API in head section: http://jsfiddle.net/s2HkR/
So how can I load the api on button click or async? Without the file being in the HEAD section. If there is a way to prevent the document.write to make the page blank or any other way. I wouldn't mind using plain js, jQuery or PHP.
EDIT:
I've set a bounty to 250 ontop of the 50 I had previously.
Orlando Leite answered a really close idea on how to make this asynch api load although some features doesn't work such as selecting dates and I am not able to set styling.
I am looking for an answer of which I will be able to use all the features so that it works as it would work if it was loading on load.
Here is the updated fiddle by Orlando: http://jsfiddle.net/cxysA/12/
-
EDIT 2 ON Gijs ANSWER:
Gijs mentioned two links onto overwriting document.write. That sounds an awesome idea but I think it is not possible to accomplish what I am trying.
I used John's Resig way to prevent document.write of which can be found here: http://ejohn.org/blog/xhtml-documentwrite-and-adsense/
When I used this method, I load the API successfuly but the snippets.js file is not loading at all.
Fiddle: http://jsfiddle.net/9HX7N/
I belive what you want is it:
function loadSkyscanner()
{
function loaded()
{
t.skyscanner.load('snippets', '1', {'nocss' : true});
var snippet = new t.skyscanner.snippets.SearchPanelControl();
snippet.setCurrency('GBP');
snippet.setDeparture('uk');
snippet.draw(document.getElementById('snippet_searchpanel'));
}
var t = document.getElementById('sky_loader').contentWindow;
var head = t.document.getElementsByTagName('head')[0];
var script = document.createElement('script');
script.type = 'text/javascript';
script.onreadystatechange= function() {
if(this.readyState == 'complete') loaded();
}
script.onload= loaded;
script.src= 'http://api.skyscanner.net/api.ashx?key=PUT_HERE_YOUR_SKYSCANNER_API_KEY';
head.appendChild(script);
}
$("button").click(function(e)
{
loadSkyscanner();
});
It's load skyscanner in iframe#sky_loader, after call loaded function to create the SearchPanelControl. But in the end, snippet draws in the main document. It's really a bizarre workaround, but it works.
The only restriction is, you need a iframe. But you can hide it using display:none.
A working example
EDIT
Sorry guy, I didn't see it. Now we can see how awful is skyscanner API. It puts two divs to make the autocomplete, but not relative to the element you call to draw, but the document.
When a script is loaded in a iframe, document is the iframe document.
There is a solution, but I don't recommend, is really a workaround:
function loadSkyscanner()
{
var t;
this.skyscanner;
var iframe = $("<iframe id=\"sky_loader\" src=\"http://fiddle.jshell.net/orlleite/2TqDu/6/show/\"></iframe>");
function realWorkaround()
{
var tbody = t.document.getElementsByTagName("body")[0];
var body = document.getElementsByTagName("body")[0];
while( tbody.children.length != 0 )
{
var temp = tbody.children[0];
tbody.removeChild( temp );
body.appendChild( temp );
}
}
function snippetLoaded()
{
skyscanner = t.skyscanner;
var snippet = new skyscanner.snippets.SearchPanelControl();
snippet.setCurrency('GBP');
snippet.setDeparture('uk');
snippet.draw(document.getElementById('snippet_searchpanel'));
setTimeout( realWorkaround, 2000 );
}
var loaded = function()
{
console.log( "loaded" );
t = document.getElementById('sky_loader').contentWindow;
t.onLoadSnippets( snippetLoaded );
}
$("body").append(iframe);
iframe.load(loaded);
}
$("button").click(function(e)
{
loadSkyscanner();
});
Load a iframe with another html who loads and callback when the snippet is loaded. After loaded create the snippet where you want and after set a timeout because we can't know when the SearchPanelControl is loaded. This realWorkaround move the autocomplete divs to the main document.
You can see a work example here
The iframe loaded is this
EDIT
Fixed the bug you found and updated the link.
the for loop has gone and added a while, works better now.
while( tbody.children.length != 0 )
{
var temp = tbody.children[0];
tbody.removeChild( temp );
body.appendChild( temp );
}
For problematic cases like this, you can just overwrite document.write. Hacky as hell, but it works and you get to decide where all the content goes. See eg. this blogpost by John Resig. This ignores IE, but with a bit of work the trick works in IE as well, see eg. this blogpost.
So, I'd suggest overwriting document.write with your own function, batch up the output where necessary, and put it where you like (eg. in a div at the bottom of your <body>'). That should prevent the script from nuking your page's content.
Edit: OK, so I had/took some time to look into this script. For future reference, use something like http://jsbeautifier.org/ to investigate third-party scripts. Much easier to read that way. Fortunately, there is barely any obfuscation/minification at all, and so you have a supplement for their API documentation (which I was unable to find, by the way -- I only found 'code wizards', which I had no interest in).
Here's an almost-working example: http://jsfiddle.net/a8q2s/1/
Here's the steps I took:
override document.write. This needs to happen before you load the initial script. Your replacement function should append their string of code into the DOM. Don't call the old document.write, that'll just get you errors and won't do what you want anyway. In this case you're lucky because all the content is in a single document.write call (check the source of the initial script). If this weren't the case, you'd have to batch everything up until the HTML they'd given you was valid and/or you were sure there was nothing else coming.
load the initial script on the button click with jQuery's $.getScript or equivalent. Pass a callback function (I used a named function reference for clarity, but you can inline it if you prefer).
Tell Skyscanner to load the module.
Edit #2: Hah, they have an API (skyscanner.loadAndWait) for getting a callback once their script has loaded. Using that works:
http://jsfiddle.net/a8q2s/3/
(note: this still seems to use a timeout loop internally)
In the skyrunner.js file they are using document.write to make the page blank on load call back... So here are some consequences in your scenario..
This is making page blank when you click on button.
So, it removes everything from page even 'jQuery.js' that is why call back is not working.. i.e main function is cannot be invoked as this is written using jQuery.
And you have missed a target 'div' tag with id = map(according to the code). Actually this is the target where map loads.
Another thing i have observed is maps is not actually a div in current context, that is maps api to load.
Here you must go with the Old school approach, That is.. You should include your skyrunner.js file at the top of the head content.
So try downloading that file and include in head tag.
Thanks