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Javascript regex returning true.. then false.. then true.. etc [duplicate]
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/^[^-_]([a-z0-9-_]{4,20})[^-_]$/gi;
You're using a g (global) RegExp. In JavaScript, global regexen have state: you call them (with exec, test etc.) the first time, you get the first match in a given string. Call them again and you get...
What is the difference between & and && in Java?
...the first operand evaluates to false since the result will be false
(x != 0) & (1/x > 1) <-- this means evaluate (x != 0) then evaluate (1/x > 1) then do the &. the problem is that for x=0 this will throw an exception.
(x != 0) && (1/x > 1) <-- this means evaluate (x...
NumPy or Pandas: Keeping array type as integer while having a NaN value
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This capability has been added to pandas (beginning with version 0.24):
https://pandas.pydata.org/pandas-docs/version/0.24/whatsnew/v0.24.0.html#optional-integer-na-support
At this point, it requires the use of extension dtype Int64 (capitalized), rather than the default dtype int64 (lowe...
数据结构与本地数据库 07：错题记录、事务与统计图 · App Inventor 2 中文网
... 数据结构与本地数据库 07：错题记录、事务与统计图 课程首页 · 全部知识课程 · 返回专题主页
这课解决什么
先预测，再运行
开始实战
新增或调整的...
Looping through array and removing items, without breaking for loop
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edited Dec 8 '17 at 17:03
community wiki
4 r...
Gradient borders
...webkit-border-image: -webkit-gradient(linear, left top, left bottom, from(#00abeb), to(#fff), color-stop(0.5, #fff), color-stop(0.5, #66cc00)) 21 30 30 21 repeat repeat;
Prooflink -- http://www.webkit.org/blog/1424/css3-gradients/
Browser support: http://caniuse.com/#search=border-image
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How to remove an element slowly with jQuery?
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answered Nov 27 '09 at 7:09
GregGreg
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How to iterate a loop with index and element in Swift
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Yes. As of Swift 3.0, if you need the index for each element along with its value, you can use the enumerated() method to iterate over the array. It returns a sequence of pairs composed of the index and the value for each item in the array. For...
How do I detect the Python version at runtime? [duplicate]
...check that you are running Python 3.x, use
import sys
if sys.version_info[0] < 3:
raise Exception("Must be using Python 3")
Here, sys.version_info[0] is the major version number. sys.version_info[1] would give you the minor version number.
In Python 2.7 and later, the components of sys.ve...
Calculate last day of month in JavaScript
If you provide 0 as the dayValue in Date.setFullYear you get the last day of the previous month:
20 Answers
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