大约有 40,000 项符合查询结果（耗时：0.0247秒） [XML]
Finding Variable Type in JavaScript
...
Use typeof:
> typeof "foo"
"string"
> typeof true
"boolean"
> typeof 42
"number"
So you can do:
if(typeof bar === 'number') {
//whatever
}
Be careful though if you define these primitives with their object wrappers (which you should ...
What does mysql error 1025 (HY000): Error on rename of './foo' (errorno: 150) mean?
...
You usually get this error if your tables use the InnoDB engine. In that case you would have to drop the foreign key, and then do the alter table and drop the column.
But the tricky part is that you can't drop the foreign key using...
Spring Test & Security: How to mock authentication?
...e properly secured. Just in case someone changes things around and accidentally removes security settings.
7 Answers
...
How to refer environment variable in POM.xml?
I am using maven as build tool. I have set an environment variable called env . How can I get access to this environment variable's value in the pom.xml file?
...
Best way to parse command-line parameters? [closed]
What's the best way to parse command-line parameters in Scala?
I personally prefer something lightweight that does not require external jar.
...
What is getattr() exactly and how do I use it?
... understand about getattr() is that getattr(li, "pop") is the same as calling li.pop .
14 Answers
...
How to execute a raw update sql with dynamic binding in rails
...
It doesn't look like the Rails API exposes methods to do this generically. You could try accessing the underlying connection and using it's methods, e.g. for MySQL:
st = ActiveRecord::Base.connection.raw_connection.prepare("update table set f1=? where f2=? and f3=?")
st.execute(f1, f2, f3)
st...
How do I expand a tuple into variadic template function's arguments?
...
Here's my code if anyone is interested
Basically at compile time the compiler will recursively unroll all arguments in various inclusive function calls <N> -> calls <N-1> -> calls ... -> calls <0> which is the last one and the compiler will o...
MongoDB/NoSQL: Keeping Document Change History
... changes to one or more specific entities in a database. I've heard this called row versioning, a log table or a history table (I'm sure there are other names for it). There are a number of ways to approach it in an RDBMS--you can write all changes from all source tables to a single table (more of...
Prepend a level to a pandas MultiIndex
...
This is especially nice for adding a level to the columns by adding axis=1, since the df.columns doesn't have the "set_index" method like the index, which always bugs me.
– Rutger Kassies
Feb 10 '17 a...