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Detecting an undefined object property
...is the special value `undefined`");
}
To check if an object does not actually have such a property, and will therefore return undefined by default when you try and access it:
if(!o.hasOwnProperty('myProperty')) {
alert("myProperty does not exist");
}
To check if the value associated with an i...
Checking if array is multidimensional or not?
...will recursively count the array. This is particularly useful for counting all the elements of a multidimensional array. count() does not detect infinite recursion.
However this method does not detect array(array()).
share...
PowerShell: Setting an environment variable for a single command only
...ariable. But if that is what you need to do you can do it this way:
$env:FOO = 'BAR'; ./myscript
The environment variable $env:FOO can be deleted later like so:
Remove-Item Env:\FOO
share
|
im...
#pragma once vs include guards? [duplicate]
... time but #pragma once is very well supported across compilers but not actually part of the standard. The preprocessor may be a little faster with it as it is more simple to understand your exact intent.
#pragma once is less prone to making mistakes and it is less code to type.
To speed up compil...
Performance difference between IIf() and If
..."Hello")
' Usage 2
Dim foo = If(result, "Alternative")
The first is basically C#'s ternary conditional operator and the second is its coalesce operator (return result unless it’s Nothing, in which case return "Alternative"). If has thus replaced IIf and the latter is obsolete.
Like in C#, VB's ...
Explicitly calling a default method in Java
...s per this article you access default method in interface A using
A.super.foo();
This could be used as follows (assuming interfaces A and C both have default methods foo())
public class ChildClass implements A, C {
@Override
public void foo() {
//you could completely override ...
What are static factory methods?
... a factory method, you would simply call the class's constructor directly: Foo x = new Foo(). With this pattern, you would instead call the factory method: Foo x = Foo.create(). The constructors are marked private, so they cannot be called except from inside the class, and the factory method is m...
Why can't the C# constructor infer type?
...type inference?
No. When you have
new Foo(bar)
then we could identify all types called Foo in scope regardless of generic arity, and then do overload resolution on each using a modified method type inference algorithm. We'd then have to create a 'betterness' algorithm that determines which of t...
PHP: How to use array_filter() to filter array keys?
... to ARRAY_FILTER_USE_KEY to filter by key instead of value:
$my_array = ['foo' => 1, 'hello' => 'world'];
$allowed = ['foo', 'bar'];
$filtered = array_filter(
$my_array,
function ($key) use ($allowed) {
return in_array($key, $allowed);
},
ARRAY_FILTER_USE_KEY
);
Cle...
Best way to load module/class from lib folder in Rails 3?
...
# Autoload lib/ folder including all subdirectories
config.autoload_paths += Dir["#{config.root}/lib/**/"]
Source: Rails 3 Quicktip: Autoload lib directory including all subdirectories, avoid lazy loading
Please mind that files contained in the lib folder...