大约有 16,000 项符合查询结果（耗时：0.0299秒） [XML]
Whether a variable is undefined [duplicate]
...eturn 'undefined' for an empty selection. It always returns an empty string (i.e. ""). .html() will return null if the element doesn't exist though.You need to do:
if(page_name != '')
For other variables that don't come from something like jQuery.val() you would do this though:
if(typeof page_...
Checking the equality of two slices
...he slice and test. Equality for slices is not defined. However, there is a bytes.Equal function if you are comparing values of type []byte.
func testEq(a, b []Type) bool {
// If one is nil, the other must also be nil.
if (a == nil) != (b == nil) {
return false;
}
if len(...
Custom Python list sorting
...uments (list
items) which should return a negative, zero or positive number
depending on whether the first argument is considered smaller than,
equal to, or larger than the second argument: cmp=lambda x,y:
cmp(x.lower(), y.lower()). The default value is None.
...
How to swap the buffers in 2 windows emacs
...
I use buffer-move for this. Now if you are working on the buffer on the left side, calling 'buf-move-right' will swap it with the one on the right. I guess this is what you want.
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How to filter rows in pandas by regex
...
Use contains instead:
In [10]: df.b.str.contains('^f')
Out[10]:
0 False
1 True
2 True
3 False
Name: b, dtype: bool
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Unique combination of all elements from two (or more) vectors
I am trying to create a unique combination of all elements from two vectors of different size in R.
5 Answers
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how to use “AND”, “OR” for RewriteCond on Apache?
...e it isn't explained very explicitly in the documentation I'll answer this by going through the sourcecode of mod_rewrite; demonstrating a big benefit of open-source.
In the top section you'll quickly spot the defines used to name these flags:
#define CONDFLAG_NONE 1<<0
#define...
How do I remove a big file wrongly committed in git [duplicate]
I did a stupid thing. Imagine that I committed a 100MB file. Then I see this and delete this file and commit again. This is a normal procedure to delete a file.
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Get Image size WITHOUT loading image into memory
...ns in the source like:
...
prefix = fp.read(16)
...
fp.seek(0)
...
but these hardly constitute reading the whole file. In fact .open simply returns a file object and the filename on success. In addition the docs say:
open(file, mode=”r”)
Opens and identifies the given image file...
Javascript swap array elements
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You only need one temporary variable.
var b = list[y];
list[y] = list[x];
list[x] = b;
Edit hijacking top answer 10 years later with a lot of ES6 adoption under our belts:
Given the array arr = [1,2,3,4], you can swap values in one line now like so:
[...