Most Popular
1500 questions
3897
votes
12 answers
Proper use cases for Android UserManager.isUserAGoat()?
I was looking at the new APIs introduced in Android 4.2.
While looking at the UserManager class I came across the following method:
public boolean isUserAGoat()
Used to determine whether the user making this call is subject to…
Ovidiu Latcu
- 70,421
- 14
- 74
- 84
3896
votes
48 answers
How do I test for an empty JavaScript object?
After an AJAX request, sometimes my application may return an empty object, like:
var a = {};
How can I check whether that's the case?
falmp
- 39,377
- 3
- 20
- 18
3890
votes
15 answers
Iterating over dictionaries using 'for' loops
d = {'x': 1, 'y': 2, 'z': 3}
for key in d:
print(key, 'corresponds to', d[key])
How does Python recognize that it needs only to read the key from the dictionary? Is key a special keyword, or is it simply a variable?
TopChef
- 40,537
- 10
- 26
- 27
3884
votes
35 answers
Delete commits from a branch in Git
I would like to know how to delete a commit.
By delete, I mean it is as if I didn't make that commit, and when I do a push in the future, my changes will not push to the remote branch.
I read git help, and I think the command I should use is git…
hap497
- 141,763
- 43
- 79
- 93
3853
votes
19 answers
Undoing a git rebase
Does anybody know how to easily undo a git rebase?
The only way that comes to mind is to go at it manually:
git checkout the commit parent to both of the branches
then create a temp branch from there
cherry-pick all commits by hand
replace the…
webmat
- 54,646
- 12
- 53
- 59
3845
votes
39 answers
What is the !! (not not) operator in JavaScript?
I saw some code that seems to use an operator I don't recognize, in the form of two exclamation points, like so: !!. Can someone please tell me what this operator does?
The context in which I saw this was,
this.vertical = vertical !== undefined ?…
Hexagon Theory
- 41,001
- 5
- 25
- 30
3840
votes
23 answers
Make an existing Git branch track a remote branch?
I know how to make a new branch that tracks remote branches, but how do I make an existing branch track a remote branch?
I know I can just edit the .git/config file, but it seems there should be an easier way.
Pat Notz
- 198,042
- 30
- 88
- 92
3837
votes
79 answers
How can I validate an email address using a regular expression?
Over the years I have slowly developed a regular expression that validates most email addresses correctly, assuming they don't use an IP address as the server part.
I use it in several PHP programs, and it works most of the time. However, from time…
acrosman
- 12,604
- 10
- 38
- 55
3805
votes
25 answers
How to insert an item into an array at a specific index (JavaScript)
I am looking for a JavaScript array insert method, in the style of:
arr.insert(index, item)
Preferably in jQuery, but any JavaScript implementation will do at this point.
tags2k
- 76,900
- 31
- 76
- 105
3790
votes
33 answers
Is there a CSS parent selector?
How do I select the element that is a direct parent of the anchor element?
As an example, my CSS would be something like this:
li < a.active {
property: value;
}
Obviously there are ways of doing this with JavaScript, but I'm hoping that…
jcuenod
- 52,209
- 14
- 61
- 102
3787
votes
11 answers
Why don't Java's +=, -=, *=, /= compound assignment operators require casting?
Until today, I thought that for example:
i += j;
Was just a shortcut for:
i = i + j;
But if we try this:
int i = 5;
long j = 8;
Then i = i + j; will not compile but i += j; will compile fine.
Does it mean that in fact i += j; is a shortcut for…
Honza Brabec
- 36,878
- 3
- 21
- 30
3769
votes
46 answers
How do I efficiently iterate over each entry in a Java Map?
If I have an object implementing the Map interface in Java and I wish to iterate over every pair contained within it, what is the most efficient way of going through the map?
Will the ordering of elements depend on the specific map implementation…
iMack
- 36,591
- 3
- 20
- 19
3750
votes
20 answers
How do I tell if a regular file does not exist in Bash?
I've used the following script to see if a file exists:
#!/bin/bash
FILE=$1
if [ -f $FILE ]; then
echo "File $FILE exists."
else
echo "File $FILE does not exist."
fi
What's the correct syntax to use if I only want to check if the file…
Bill the Lizard
- 386,424
- 207
- 554
- 861
3726
votes
44 answers
Loop through an array in JavaScript
In Java, you can use a for loop to traverse objects in an array as follows:
String[] myStringArray = {"Hello", "World"};
for (String s : myStringArray) {
// Do something
}
Can I do the same in JavaScript?
Mark Szymanski
- 53,532
- 23
- 67
- 87
3715
votes
31 answers
Checking if a key exists in a JavaScript object?
How do I check if a particular key exists in a JavaScript object or array?
If a key doesn't exist, and I try to access it, will it return false? Or throw an error?
Adam Ernst
- 49,494
- 18
- 56
- 71