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MongoDB: How to query for records where field is null or not set?
...not set then:
db.emails.count({sent_at: {$exists: false}})
If its there and null, or not there at all:
db.emails.count({sent_at: null})
Refer here for querying and null
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Efficient way to return a std::vector in c++
How much data is copied, when returning a std::vector in a function and how big an optimization will it be to place the std::vector in free-store (on the heap) and return a pointer instead i.e. is:
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What is the difference between a function expression vs declaration in JavaScript? [duplicate]
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@JCM AFAIK, the name property is not part of ECMAScript and is only implemented in some browsers. Function.name at MDN
– Zach Lysobey
Apr 2 '13 at 20:55
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What does the 'static' keyword do in a class?
...n the example given, main does not know which instance of the Hello class (and therefore which instance of the Clock class) it should refer to. static members can only refer to static members. Instance members can, of course access static members.
Side note: Of course, static members can access ins...
What are all the valid self-closing elements in XHTML (as implemented by the major browsers)?
...nly) browsers to accept XHTML 1.0 documents by following the
guidelines, and serving them as text/html. Therefore, documents served as
text/html should be treated as HTML and not as XHTML.
It's a very common pitfall, because W3C Validator largely ignores that rule, but browsers follow it relig...
Why does [5,6,8,7][1,2] = 8 in JavaScript?
...e second [...] cannot be an array, so it’s an array subscript operation. And the contents of a subscript operation are not a delimited list of operands, but a single expression.
Read more about the comma operator here.
sh...
Markdown and including multiple files
... image to the right or left. As to your question, there's no markdown command to include a single link from one file to another in any version of markdown (so far as I know).
The closest you could come to this functionality is Pandoc. Pandoc allows you to merge files as a part of the transforma...
For loop for HTMLCollection elements
...x. So, to get the value from the pseudo-array, you'd have to do list[key] and to get the id, you'd do list[key].id. But, you should not be doing this with for/in in the first place.
Summary (added in Dec 2018)
Do not ever use for/in to iterate a nodeList or an HTMLCollection. The reasons to avo...
Installing Python packages from local file system folder to virtualenv with pip
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It do help. And we can use -i option of pip to treat it as a local PyPI.
– diabloneo
Jun 12 '15 at 7:37
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github: No supported authentication methods available
i use github and have successfully added and synched files on my laptop in the past.
16 Answers
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