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What's the scope of a variable initialized in an if statement?
... function, class, or module in which they're assigned. Control blocks like if and while blocks don't count, so a variable assigned inside an if is still scoped to a function, class, or module.
(Implicit functions defined by a generator expression or list/set/dict comprehension do count, as do lambd...
Android Fragment handle back button press [duplicate]
...ace( R.id.fragment, new MyFragment() ).addToBackStack( "tag" ).commit();
If you require more detailed control (i.e. when some Fragments are visible, you want to suppress the back key) you can set an OnKeyListener on the parent view of your fragment:
//You need to add the following line for this s...
How to determine whether an object has a given property in JavaScript
...
Object has property:
If you are testing for properties that are on the object itself (not a part of its prototype chain) you can use .hasOwnProperty():
if (x.hasOwnProperty('y')) {
// ......
}
Object or its prototype has a property:
You ca...
How to check if the user can go back in browser history or not
I want using JavaScript to see if there is history or not, I mean if the back button is available on the browser or not.
18...
Check, using jQuery, if an element is 'display:none' or block on click
...hidden');
visibleElements = $(':visible');
To check particular element.
if($('#yourID:visible').length == 0)
{
}
Elements are considered visible if they consume space in the document.
Visible elements have a width or height that is greater than zero,
Reference
You can also use is() wi...
How to determine if object is in array [duplicate]
I need to determine if an object already exists in an array in javascript.
11 Answers
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What is the proper way to check if a string is empty in Perl?
I've just been using this code to check if a string is empty:
6 Answers
6
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Why is there no logical xor in JavaScript?
...ul, but in all my years of programming I have never needed a logical XOR.
If you have two boolean variables you can mimic XOR with:
if (a != b)
With two arbitrary variables you could use ! to coerce them to boolean values and then use the same trick:
if (!a != !b)
That's pretty obscure though...
Default value of a type at Runtime [duplicate]
... only need to account for two cases:
object GetDefaultValue(Type t)
{
if (t.IsValueType)
return Activator.CreateInstance(t);
return null;
}
(Because value types always have a default constructor, that call to Activator.CreateInstance will never fail).
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Checking if a key exists in a JavaScript object?
How do I check if a particular key exists in a JavaScript object or array?
22 Answers
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