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How do I check in JavaScript if a value exists at a certain array index?
Will this work for testing whether a value at position index exists or not, or is there a better way:
18 Answers
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Reference — What does this symbol mean in PHP?
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Incrementing / Decrementing Operators
++ increment operator
-- decrement operator
Example Name Effect
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++$a Pre-increment Increments $a by one, then returns $a.
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How do I concatenate or merge arrays in Swift?
...g a new array
let c = a + b
print(c) // [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
or append one array to the other with += (or append):
a += b
// Or:
a.append(contentsOf: b) // Swift 3
a.appendContentsOf(b) // Swift 2
a.extend(b) // Swift 1.2
print(a) // [1.0, 2.0, 3.0, 4.0, 5.0, 6.0]
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Regex exactly n OR m times
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There is no single quantifier that means "exactly m or n times". The way you are doing it is fine.
An alternative is:
X{m}(X{k})?
where m < n and k is the value of n-m.
share
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MongoDB aggregation framework match OR
Is it possible to do an OR in the $match?
2 Answers
2
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what is “strict mode” and how is it used?
...ve been looking over the JavaScript reference on the Mozilla Developer Network, and I came across something called "strict mode" . I read it over and I'm having trouble understanding what it does. Can someone briefly explain (in general) what its purpose is and how it is useful?
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Shell equality operators (=, ==, -eq)
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It's the other way around: = and == are for string comparisons, -eq is for numeric ones. -eq is in the same family as -lt, -le, -gt, -ge, and -ne, if that helps you remember which is which.
== is a bash-ism, by the way. It's better to use the POSIX =. In bash the t...
Extracting text OpenCV
...e elements (inspired from a LPD):
#include "opencv2/opencv.hpp"
std::vector<cv::Rect> detectLetters(cv::Mat img)
{
std::vector<cv::Rect> boundRect;
cv::Mat img_gray, img_sobel, img_threshold, element;
cvtColor(img, img_gray, CV_BGR2GRAY);
cv::Sobel(img_gray, img_sobel, ...
Depend on a branch or tag using a git URL in a package.json?
Say I've forked a node module with a bugfix and I want to use my fixed version, on a feature branch of course, until the bugfix is merged and released.
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Why are these constructs using pre and post-increment undefined behavior?
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C has the concept of undefined behavior, i.e. some language constructs are syntactically valid but you can't predict the behavior when the code is run.
As far as I know, the standard doesn't explicitly say why the concept of undefined behavior exists. In my min...