大约有 40,000 项符合查询结果（耗时：0.0612秒） [XML]
How to efficiently count the number of keys/properties of an object in JavaScript?
...t only iterates through the object but also creates a whole new array with all its keys, so it completely fails at answering the question.
– GetFree
Jun 22 '12 at 14:28
43
...
Get name of object or class
...(function(){}); new myclass prints myclass {}
– Hugh Allen
May 26 '14 at 4:09
...
SQL to determine minimum sequential days of access?
...
@Artem: That was what I initially thought but when I thought about it, if you have an index on (UserId, CreationDate), the records will show up consecutively in the index and it should perform well.
– Mehrdad Afshari
...
MongoDB/Mongoose querying at a specific date?
...onents. To query those times you need to create a date range that includes all moments in a day.
db.posts.find( //query today up to tonight
{"created_on": {"$gte": new Date(2012, 7, 14), "$lt": new Date(2012, 7, 15)}})
s...
Best way to iterate through a Perl array
...ay elements occurs. ($_ is aliased to the element in #1, but #2 and #3 actually copy the scalars from the array.)
#5 might be similar.
In terms memory usage: They're all the same except for #5.
for (@a) is special-cased to avoid flattening the array. The loop iterates over the indexes of the array...
Python: most idiomatic way to convert None to empty string?
...
If you actually want your function to behave like the str() built-in, but return an empty string when the argument is None, do this:
def xstr(s):
if s is None:
return ''
return str(s)
...
Why can't C compilers rearrange struct members to eliminate alignment padding? [duplicate]
...
There are multiple reasons why the C compiler cannot automatically reorder the fields:
The C compiler doesn't know whether the struct represents the memory structure of objects beyond the current compilation unit (for example: a foreign library, a file on disc, network data, CPU page ...
What is a proper naming convention for MySQL FKs?
...constraints. If a name is not given, InnoDB creates a unique name automatically.
In any case, this is the convention that I use:
fk_[referencing table name]_[referenced table name]_[referencing field name]
Example:
CREATE TABLE users(
user_id int,
name varchar(100)
);
CREATE T...
Remove duplicates from an array of objects in JavaScript
...) dot notation. Yours is ES5 syntax. The others are mostly ES6 (ECMA2015). All are valid in 2017. See jaredwilli's comment.
– agm1984
Nov 15 '17 at 9:20
...
Why is there no xrange function in Python3?
...Some performance measurements, using timeit instead of trying to do it manually with time.
First, Apple 2.7.2 64-bit:
In [37]: %timeit collections.deque((x for x in xrange(10000000) if x%4 == 0), maxlen=0)
1 loops, best of 3: 1.05 s per loop
Now, python.org 3.3.0 64-bit:
In [83]: %timeit collec...