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How can I check for “undefined” in JavaScript? [duplicate]
...cript 5th ed., and undefined is non-writable.
if (window.myVar) will also include these falsy values, so it's not very robust:
false
0
""
NaN
null
undefined
Thanks to @CMS for pointing out that your third case - if (myVariable) can also throw an error in two cases. The first is when the variabl...
How to initialize an array in one step using Ruby?
...are required
# or
array = *('1'..'3') # parentheses not required, but included for clarity
For arrays of whitespace-delimited strings, you can use Percent String syntax:
array = %w[ 1 2 3 ]
You can also pass a block to Array.new to determine what the value for each entry will be:
array = ...
Releasing memory in Python
...' for x in range(10**7)]
mem1 = proc.get_memory_info().rss
# unreference, including x == 9999999
del foo, x
mem2 = proc.get_memory_info().rss
# collect() calls PyInt_ClearFreeList()
# or use ctypes: pythonapi.PyInt_ClearFreeList()
gc.collect()
mem3 = proc.get_memory_info().rss
pd = lambda x2, x1:...
Is there a way to view past mysql queries with phpmyadmin?
...SELECT * FROM general_log must be queried inside mysql table else you must include tablename: SELECT * FROM mysql.general_log
– siggi_pop
Aug 17 '17 at 12:59
...
how to check if a form is valid programmatically using jQuery Validation Plugin
... valid() not a function add the plugin to your file since its a plugin not included in jquery library eg. <script src="https://cdn.jsdelivr.net/jquery.validation/1.16.0/jquery.validate.min.js"></script>
– StackEdd
Jan 15 at 14:50
...
ObservableCollection not noticing when Item in it changes (even with INotifyPropertyChanged)
...
I've put together what I hope is a pretty robust solution, including some of the techniques in other answers. It is a new class derived from ObservableCollection<>, which I'm calling FullyObservableCollection<>
It has the following features:
It adds a new event, ItemPr...
When to use IMG vs. CSS background-image?
...if you intend to have
people print your page and you want the image to be included by default.
—JayTee
Use IMG (with alt text) when the image has an important semantic meaning, such as a warning icon. This ensures that the meaning of the image can be communicated in all user-agents, including sc...
Are there any disadvantages to always using nvarchar(MAX)?
..., is not true, the value gets pushed out of row based on may more factors, including sp_tableoptions: msdn.microsoft.com/en-us/library/ms173530.aspx. VARCHAR(255) types can also b pushed out of row, the 'overhead' mentioned may be exactly the same for MAX and 255. It compares MAX types with TEXT typ...
Is delete this allowed?
...[class.dtor]/13):
At the point of definition of a virtual destructor (including an implicit definition (15.8)), the non-array deallocation function is determined as if for the expression delete this appearing in a non-virtual destructor of the destructor’s class (see 8.3.5).
That tends to su...
How to print third column to last column?
... printing an internal range is also possible: ``` # from $3 (included) to $6 (excluded); echo "1,2,3,4,5,6,7,8,9" | awk 'BEGIN{FS=",";OFS=","}{ print substr($0, index($0,$3), length($0)-index($0,$6)-1) }'; # gives 3,4,5```
– splaisan
Nov 27 '19 a...