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Checking if a key exists in a JavaScript object?
... testing whether a key exists. What if the key exists but the value is actually undefined?
var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!
You should instead use the in operator:
"key" in obj // true, regardless of the actual value
If you want to check if a...
What requests do browsers' “F5” and “Ctrl + F5” refreshes generate?
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Generally speaking:
F5 may give you the same page even if the content is changed, because it may load the page from cache. But Ctrl-F5 forces a cache refresh, and will guarantee that if the content is changed, you will get the ne...
How do I auto-submit an upload form when a file is selected?
I have a simple file upload form. How do I make it submit automatically when a file has been selected? I don't want the user to have to click the Submit button.
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ipython notebook clear cell output in code
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Using the clear_output(wait=True) will generally make the result nicer if you have clear_output inside a loop.
– Toke Faurby
Jun 8 '17 at 23:49
1
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Trigger 404 in Spring-MVC controller?
...lic class SomeController {
@RequestMapping.....
public void handleCall() {
if (isFound()) {
// whatever
}
else {
throw new ResourceNotFoundException();
}
}
}
...
How do I kill background processes / jobs when my shell script exits?
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but can also be used to execute something if the shell exits:
trap "killall background" EXIT
It's a builtin, so help trap will give you information (works with bash). If you only want to kill background jobs, you can do
trap 'kill $(jobs -p)' EXIT
Watch out to use single ', to prevent the sh...
What is the best way to test for an empty string with jquery-out-of-the-box?
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Based on David's answer I personally like to check the given object first if it is a string at all. Otherwise calling .trim() on a not existing object would throw an exception:
function isEmpty(value) {
return typeof value == 'string' && !value.t...
How do I auto-reload a Chrome extension I'm developing?
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You can use "Extensions Reloader" for Chrome:
Reloads all unpacked extensions using the extension's toolbar button or by browsing to "http://reload.extensions"
If you've ever developed a Chrome extension, you might have wanted to
automate the process of reloading your unp...
Notification passes old Intent Extras
...gIntent contentIntent = PendingIntent.getActivity(context, UNIQUE_INT_PER_CALL, notificationIntent, 0);
intents are not created if you send the same params. They are reused.
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.NET unique object identifier
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I guess for lookups you'd have to iterate over all the references you track: WeakReference to the same object are not equal to each other, so you can't really do much else.
– Roman Starkov
Apr 23 '10 at 10:31
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