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How do I perform the SQL Join equivalent in MongoDB?
...rect. The new $lookup operator added to the aggregation pipeline is essentially identical to a left outer join:
https://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <...
Remove empty elements from an array in Javascript
...ll return you a new array with the elements that pass the criteria of the callback function you provide to it.
For example, if you want to remove null or undefined values:
var array = [0, 1, null, 2, "", 3, undefined, 3,,,,,, 4,, 4,, 5,, 6,,,,];
var filtered = array.filter(function (el) {
...
Time complexity of Sieve of Eratosthenes algorithm
...oose upper-bound is n(1+1/2+1/3+1/4+1/5+1/6+…1/n) (sum of reciprocals of all numbers up to n), which is O(n log n): see Harmonic number. A more proper upper-bound is n(1/2 + 1/3 + 1/5 + 1/7 + …), that is sum of reciprocals of primes up to n, which is O(n log log n). (See here or here.)
The "find...
How to perform Callbacks in Objective-C
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How to convert .pfx file to keystore with private key?
...entcert.jks -deststoretype JKS
Using JDK 1.5 or below
OpenSSL can do it all. This answer on JGuru is the best method that I've found so far.
Firstly make sure that you have OpenSSL installed. Many operating systems already have it installed as I found with Mac OS X.
The following two commands c...
Python read-only property
...
Generally, Python programs should be written with the assumption that all users are consenting adults, and thus are responsible for using things correctly themselves. However, in the rare instance where it just does not make sens...
.net localhost website consistently making get arterySignalR/poll?transport=longPolling&connectionTo
...ewed the default.aspx page with the Firefox browser. When I check the net calls it has made, I see it making constant calls to:
...
Getting the max value of an enum
...ution was given. Also if you want to get the enum value use Convert.ToInt32() afterwards. This is for the google results.
– jdelator
Oct 15 '08 at 1:15
55
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How can I use xargs to copy files that have spaces and quotes in their names?
...
You can combine all of that into a single find command:
find . -iname "*foobar*" -exec cp -- "{}" ~/foo/bar \;
This will handle filenames and directories with spaces in them. You can use -name to get case-sensitive results.
Note: The ...
How do JavaScript closures work?
...clared outside the function, regardless of when and where the function is called.
If a function was called by a function, which in turn was called by another function, then a chain of references to outer lexical environments is created. This chain is called the scope chain.
In the following code, in...