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When is null or undefined used in JavaScript? [duplicate]
I am really confused as to when JavaScript returns null or undefined . Also different browsers seem to be returning these differently.
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Renaming table in rails
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You would typically do this sort of thing in a migration:
class RenameFoo < ActiveRecord::Migration
def self.up
rename_table :foo, :bar
end
def self.down
rename_table :bar, :foo
end
end
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RESTful Services - WSDL Equivalent
... still don't understand why there isn't the "WSDL" equivalent in the REST world. I have seen posts saying there is "no need" for the WSDL or that it would be redundant In the REST world, but I don't understand why. Isn't it always useful to programmatically bind to a definition and create proxy cl...
How to test if a double is an integer
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if ((variable == Math.floor(variable)) && !Double.isInfinite(variable)) {
// integer type
}
This checks if the rounded-down value of the double is the same as the double.
Your variable could have an int or double value and Math.floor(v...
The static keyword and its various uses in C++
The keyword static is one which has several meanings in C++ that I find very confusing and I can never bend my mind around how its actually supposed to work.
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Batch renaming files with Bash
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You could use bash's parameter expansion feature
for i in ./*.pkg ; do mv "$i" "${i/-[0-9.]*.pkg/.pkg}" ; done
Quotes are needed for filenames with spaces.
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Perl flags -pe, -pi, -p, -w, -d, -i, -t?
I have seen lots of ways of running Perl code or scripts, with different flags. However, when I try to google for what each flag means, I mainly get results to generic Perl sites and no specific information regarding the flags or their use is found there.
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How to convert a boolean array to an int array
...ot even be necessary to do this, depending on what you're using the array for. Bool will be autopromoted to int in many cases, so you can add it to int arrays without having to explicitly convert it:
>>> x
array([ True, False, True], dtype=bool)
>>> x + [1, 2, 3]
array([2, 2, 4]...
Can I use non existing CSS classes?
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"CSS class" is a misnomer; class is an attribute (or a property, in terms of scripting) that you assign to HTML elements. In other words, you declare classes in HTML, not CSS, so in your case the "target" class does in fact exist on those specific elements, and your markup i...
Can I have an IF block in DOS batch file?
...1 line if statement body? I think I found somewhere that I could use () for an if block just like the {} used in C-like programming languages, but it is not executing the statements when I try this. No error message either. This my code:
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