Develop Reference

Really strange Javascript / PHP Behavior

from a webpage, I want to allow users to create a cvs file on the server and download it, generated by PHP ( header('Content-Description: File Transfer') ).
function download_csv_file(){document.location='?action=download_file';}
It works like a charm. File is created and download start automatically like it should be.
But, if I add any other js events/scripts in the JS function (on the same line on a new line), the file is created on the server, but no download.
Really strange, a simple comment on the next line break the process too... But if the comment is on the same line, it works ! Crazy !!!
function download_csv_file(){
document.location='?action=download_file';
// Simple comment
}
Don't work !
function download_csv_file(){
document.location='?action=download_file'; // Simple comment
}
Works !!!
But if I add real code on the same line (instead a comment) it doesn't work.
Any explanation or idea what I can try or search for ?..
Same behavior in Chrome and Firefox

document.location
tells the browser to go to a different URL. Therefore it stops executing anything at the current URL and navigates to a new one instead. And of course that means that any JavaScript code following that command will be ignored.
N.B. since your new URL happens to download a file, it may be that you can still see the previous page in the background, which may lead you to believe that it's still the current page.
You can potentially get round this by using window.open to visit the download URL in a different tab instead.
P.S. Regarding the issue with comments...did you check for any errors in your browser's Console when that occurred? I can't reproduce the problem: https://codepen.io/ADyson82/pen/dyGYQrd

jquery conflict with my website

I layout'd a page and on my server which is it hostgator works extremely fine, using the jQuery mobile components:
http://brunolustro.com/roger/teste/cadastro.html
But my friend who is programming the page wanted me to insert the newest CDNs from either jQuery and jQuery Mobile:
And this is what the page looks like when I insert those codes:
http://brunolustro.com/roger/test/cadastro.html
Do you know how to fix this?
Regards,
Bruno

When working with JavaScript or jQuery on your website - if something isn't working as you intend - the first thing you should do is check the browser console to see if anything is being logged there.
To check the browser console:
Hit F12 on your keyboard. When the developer tools open, choose the console tab, its placed in the toolbar at the top of the new window.
In the console you will see a few errors in red with error codes (404). A 404 means the requested file wasn't found.
This tells us that your reference to jQuery isn't correct. This could be because the file path you've written isn't correct, or that you haven't deployed those files correctly to your site.
Check your file paths you've referenced and make sure the file is on your server. Once both are correct - the errors should go away.
Here's a link to view more about developer tools: https://developer.chrome.com/devtools#console

Check following files in your "test/js" and "teste/js" folders, because i've got 404 not found error:
jquery-2.0.3.min.js
modernizr-2.6.2.min.js
jquery.mobile-1.4.5.min.map

Javascript in asp.net MVC... Beginner issue

I created an Asp.Net MVC Internet Aplication and in my Index view of the Home Controller I have this
This is the first line, before the script results.
<script type="text/javascript" src="~/Script/Teste.js"></script>
<br />
This line comes after the script.
In my Teste.js I have this:
document.write("Yes! I am now a JavaScript coder!");
But nothing happens. If I change the src attribute and put some random name src="aaaa", despite the fact "aaaa" doesnt exist, I get no error in runtime.

EDIT
Also, check your path again. The default MVC templates in VS create a folder called Scripts, not Script. ("~/Scripts/teste.js")
Per the comment below, this was not the root cause of the issue, but in other cases can easily bite new JavaScript developers.
Most likely, your document.write function is firing before the document is ready, leading to the appearance that nothing is happening. Try the following in your Teste.js file
window.onload = function ()
{
document.write("Yes! I am now a JavaScript coder!");
//or even better as a test
alert("This alert was called");
}
Check the source of your page as well, it could be the document is being written to, you just can't see it due to markup/page styling.
As for you second issue, there will be no 'Runtime Exception' thrown if you reference a non-existent file. If you are using tools like Firebug or Chrome's developer tools, you should see a request to http://siteDomain/Scripts/aaaa.js with a response of 404, not found.

You generally should avoid using document.write() unless you absolutely have to use it for some reason... I don't think I've ever come across such a situation, and write a lot of Javascript.
Try this:
1) Put this in your HTML:
<script src="/scripts/teste.js"></script>
2) Put this in your JS:
alert('Yes! I am now a JavaScript coder!');
3) Open Chrome since it makes it easy to look for external resources loading and open the Network tab in Developer Tools (click the menu button at top-right, Tools > Developer Tools, Network tab).
4) Run your project and copy/paste the URL in the browser that comes up into this Chrome window, and hit enter.
When your page loads one of 2 things will happen:
A) You'll get the alert box you wanted or
B) You'll find out why it isn't loading because the Network tab will show the browser attempting to fetch teste.js and failing in some fashion, for example a 404, which would indicate you've got a typo in the path, or the script isn't where you thought it was, etc.

Put the following line at the very end of your document. There should not be anything after. Then try to load the page.
<script type="text/javascript" src="~/Script/Teste.js"></script>
Also, try pressing F12 once the page loads to see the source. Check if you script is there.

In MVC, the tilde is used to refer to the root URL of your application. However, it cannot normally parse this information. If you write:
<script src="~/Script/Teste.js"></script>
The lookup will fail, because the ~ means nothing special in HTML. If you're using Razor as your view engine (not ASPX), you need to wrap that call in Url.Content like so:
<script src="#Url.Content(~/Script/Teste.js)"></script>
Doing this will ensure a valid URL is provided to the browser.
With that in mind, you need to check that you have the file name and folder name both correct. You also need to ensure that the file is being deployed with your application. You can do this my opening the properties panel while the file is selected in the Solution Explorer and pressing F4.

Facebook like button in site that uses post message spams console

I have a site that uses a lot of postMessage communication between iframes. Putting a Facebook like button in my site causes my debug console to get spammed with messages like
Received message of type object from [domain], expected a string.
This makes development very difficult. Is there any way to prevent this extra logging from occurring? I am new to using facebooks apis so I'm hoping I'm just missing something simple. They can't possibly assume that no one besides them will ever use postmessage.
Thanks!

Actually, disabling console.log is a horrible answer. What if we want to use console.log, but just want to stop the spamming error message? What is causing it? How do we actually fix it?

Actually that's not an extra logging. It's from the Facebook SDK. Simply you can uglify the sdk for removing all console from the library.
1.Download the sdk. https://connect.facebook.net/en_US/sdk.js
2.Uglify it for removing console logging (production version.)
https://github.com/mishoo/UglifyJS
3.Use it in your site.
Another link which may help you:
http://elijahmanor.com/grunt-away-those-pesky-console-log-statements/

You could simply "unset" the console.log function, by doing something like:
console.log = function(){}
Save it in another variable first, for example:
var originalLog = console.log;
Now when the Facebook API tries to use the log function nothing will happen. If you need to use the log function, just enable it first by setting it back to your saved originalLog variable and unset it when you are done using it. Unhandled errors will still show up in your console, regardless of what you have done to the log function.

In my case this was caused by the FVD Video Downloader extension, so maybe you should disable all browser extensions and see if that solves the issue, then enable them back one by one to find the culprit.

console.log doesn't print the message to the firebug console?

I am facing this weird problem. The WebApp I'm debugging right now, is invoking the javascript console.log/console.log/error/debug/etc., the Firebug console however, doesn't print them at all.
This application uses Dojo/Dijit toolkit. Not sure if there is anything special about it
It doesn't appear to be a problem with the Browser, I tried another simple web-page with a console.debug call, and the message appears on the console as expected.
Please advise about what should I look for. I have also tried Chrome/IE.
Thanks in Advance/

console is not write protected, it can be replaced with anything. You could try
alert(console.log.toString());
to find out what console.log really is
Edit:
A better method would be
var originalConsole = console;
// now include your library
// ...
originalConsole.log(console.log);
In Firebug, clicking on the function takes you directly to its definition.

did you try window.console.log()? Maybe you are not in window scope

In case like this do not forget to check if "Logging" is enabled or active at your console of browser.

Just to update this question -:
Ensure that firebug is Enabled - - > On for all Web Pages.
Reload the application.
Then in the firebug panel - - > Console - - > All.
All the console.log messages will appear.