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How to check 'undefined' value in jQuery
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JQuery library was developed specifically to simplify and to unify certain JavaScript functionality.
However if you need to check a variable against undefined value, there is no need to invent any special method, since JavaScript has a typeof operator, whic...
Python list subtraction operation
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Use a list comprehension:
[item for item in x if item not in y]
If you want to use the - infix syntax, you can just do:
class MyList(list):
def __init__(self, *args):
super(MyList, self).__init__(args)
def __sub__(self, other):
return self.__c...
How to check for an undefined or null variable in JavaScript?
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You have to differentiate between cases:
Variables can be undefined or undeclared. You'll get an error if you access an undeclared variable in any context other than typeof.
if(typeof someUndeclaredVar == whatever) // works
if(someUnd...
How to check if a string contains an element from a list in Python
...se a generator together with any, which short-circuits on the first True:
if any(ext in url_string for ext in extensionsToCheck):
print(url_string)
EDIT: I see this answer has been accepted by OP. Though my solution may be "good enough" solution to his particular problem, and is a good genera...
How to tell if a file is git tracked (by shell exit code)?
Is there a way to tell if a file is being tracked by running some git command and checking its exit code?
8 Answers
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add column to mysql table if it does not exist
... MySQL prior to 5.0. Nor are stored procedures supported prior to 5.0, so if you need to support MySQL 4.1, this solution isn't good.
One solution used by frameworks that use database migrations is to record in your database a revision number for the schema. Just a table with a single column and ...
How do you check if a selector matches something in jQuery? [duplicate]
In Mootools, I'd just run if ($('target')) { ... } . Does if ($('#target')) { ... } in jQuery work the same way?
11 Ans...
Checking if a folder exists using a .bat file [closed]
I would like to be able to check if a certain folder (FolderA) exists and if so, for a message to be displayed and then the batch file to be exited.
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Compare two objects' properties to find differences?
...s tricky.
public bool ReflectiveEquals(object first, object second)
{
if (first == null && second == null)
{
return true;
}
if (first == null || second == null)
{
return false;
}
Type firstType = first.GetType();
if (second.GetType() != firstT...
Using parameters in batch files at Windows command line
...r tokens that you can use:
%0 is the executable (batch file) name as specified in the command line.
%* is all parameters specified in the command line -- this is very useful if you want to forward the parameters to another program.
There are also lots of important techniques to be aware of in ad...