I call my JavaScript files like this:
jsfilename.js?v=1234
And on each request I change the v parameter. Second request:
jsfilename.js?v=4567
Is that a way to debug on Chrome DevTools with this variable name?
Because now, every time I create a breakpoint and refresh the page, my breakpoint looses reference.
Use statement debugger in your JS code.
Don't forget to remove it after all ;-)
I would use console.log() to report back the variable name every time I need it. This should be able to show you the exact point where your script fails.
You can also disable cache while DevTool is open. Go to settings (click the 3 dots on the right and select settings) In this way you should refresh the page and not keep cache.
Errors are as mentioned in the other answer generally shown iin the console:-)
usually, you put ?v=xyz so that you can bypass browser cache [if the parameter is different, the browser gets the file from the server and not the cache].
this is used mostly whan you have to deal with CDN.
For debugging purposes, the Javascript debugger has an option to disable cache [open debug, go to settings; is the first checkbox in the "General" panel]
of course you can have problems in breakpoint persistence if the filename is diffeerent; so, as long as you're debugging, just disable cache, and, of course, don't place js file on CDN unless they're in their stable release;
Related
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
I have been sitting here for almost an hour here to test the website I'm building. Since I wanted to see the new changes from my code I reloaded, but it was reloading old one. I opened the devetools to hard reload and empy cache hard reload, they both load my old code. I went to incognito mode and it did the same thing. I went to devtools again to disable the cache from the settings and checked the disable cache in the network tab; it still cache my old code. Add-ons to clear the cache didn't work as well. Man, I haven't had this problem before and it only happened last night and it's worst today.
I'm so lost now since chrome doesn't load my new changes from my javascript file. Is there a solution for this?
One solution for this problem is to force reloading the resource in order to avoid the cache. You can get this modifying the url with http get parameters:
Change:
<script src="myscripts.js"></script>
to:
<script src="myscripts.js?newversion"></script>
Where newversion can be any string as it will be ignored. A useful option is to use the date, or version, of your code.
I found this workaround particularly useful when I came across this same problem and wanted to ensure that all clients (not just my own browser!) would run the new version of the code.
I think there's an even better way:
You can use PHP to add the last modification date of your JavaScript file to the URI of that file.
<script src="js/my-script.js?<?php echo filemtime('js/my-script.js'); ?>">
</script>
The browser will receive:
<script src="js/my-script.js?1524155368"></script>
The URI of the file will automatically change if the file is updated.
This way the browser can still cache unchanged files while recognizing changes instantly.
Are you using any type of compilation tools (like gulp or grunt)? It's possible that there is an error in your code, and the tool is not compiling the updated code.
Otherwise, the solution #airos suggested should work. Appending any unique query string to the reference of your JS will always serve a fresh copy on first reload (since the browser will be caching a new URL).
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.
We have ASP.NET application in which we have used the YUI to generated the popup for user interface. Now when I amd testing the locally isntalled site the popups are comming correctctly withoug any error and also getting displayed correctly on all the browwsers (including IE 7/8/9).
However when the site is exposed on the server and i tried to test it from the outside network the YUI popup's are not getting genrated correclty like if some Javascript or CSS are not getting loaded or are cached. Generally Ctr+F5 does the trick to flush local cache and to fix the issue we have added query parameters xyz.css?v=10 trick. But its not working. Now this issue is showing only on the IE(6/7/8/9) and other browsers are working correctly. To check the issue i again logged into the production box and found that popup is appearing correctly on IE also.
Now i am not having clue how it could possibly happen. Does any one has came across anything like this? What could be the cause of the issue and how to fix it ?
Thanks
As far as I know, IE caches GET responses.
The xyz.css?v=10 trick is used when you want it to use cached CSS but only as long as it is the same version. Whenever you change something in the css you need to change the url (ie xyz.css?v=20).
If you want IE to NEVER use the cached css, you need the URL to look different everytime. you can do that by adding some timestamp to the url.
something like:
xyz.css?v=201201180600123
(201201180600123 is a timestamp)
I'm trying to debug a Javascript written in the Mootools framework. Right now I am developing a web application on top of Rails and my webserver is the rails s that boots WEBrick.
When I modify a particular tree.js file thats called with in one a mootools init script,
require: {
css: [MUI.path.plugins + 'tree/css/style.css'],
js: [MUI.path.plugins + 'tree/scripts/tree.js'],
onload: function(){
if (buildTree) buildTree('tree1');
}
},
the changes are not loaded as the headers being sent to the client are Last Modified: 10 July, 2010..... which is obviously not true since I just modified the file.
How do I get rid of this annoying caching. If I go directly to the script in my browser (Chrome) it doesn't show the changes until I hit refresh, but this doesn't fix my problem when I go back to my application and hit refresh, it still loads the pre-modified script.
This has happen to me also in FF, I think it is a cache header sent by the server or the browser itself.
Anyway a simple way to avoid this problem while in development is adding a random param to the file name of the script.
instead of calling 'tree/scripts/tree.js' use 'tree/scripts/tree.js?'+random that should invalidate all caches.
As frisco says, adding a random number in development does the trick but you will likely find that the problem still affects you production. You want to push new JavaScript changes to your users but can't until their browsers stop caching the file. In order to do this, just get the files mtime and add that as the random string. This will only change when the file is modified and so the JavaScript will be loaded from cache if it has not been changed or it will be loaded from the server, if it has.
PHP has the function filemtime but as I'm not familiar with Ruby, I'm afraid I can't help you further in that direction (sorry!). However, this answer seems to accomplish what you want.
Try the Ctrl+F5 trick. To avoid hitting browser cache.
More info here:
What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?