用正则表达式将多个字符替换为一个字符 [英] Replace multiple characters by one character with regex

问题描述

我有这个字符串:

var str = '#this #is____#a test###__'

我想用(#)替换所有字符(#，_)，所以例外的输出是:

I want to replace all the character (#,_) by (#) , so the excepted output is :

'#this #is#a test#'

注意:我不知道字符串中(#)或(_)有多少顺序

Note : I did not knew How much sequence of (#) or (_) in the string

我尝试什么:

我尝试写:

var str = '#this #is__ __#a test###__'
str = str.replace(/[#_]/g,'#')
alert(str)

但是输出是:

#this #is## ###a test#####

我在线尝试

我尝试将(*)用于序列，但没有用:

I try to use the (*) for sequence But did not work :

var str = '#this #is__ __#a test###__'
str = str.replace(/[#_]*/g,'#')
alert(str)

那么我如何获得我的例外输出?

so How I can get my excepted output ?

推荐答案

编写良好的RegEx可以轻松解决您的问题.引用莫希特的答案有一个起点:

A well written RegEx can handle your problem rather easily. Quoting Mohit's answer to have a startpoint:

var str = '#this #is__ __#a test###__';
var formattedStr = str.replace(/[#_,]+/g, '#');
console.log( formattedStr );

第2行:
将替换方法在str上的结果放入formattedStr中.
替换工作如何?第一个参数是字符串或RegEx.
注意:Javascript中的RegExps是RegExp类型的对象，而不是字符串.所以写

Line 2:
Put in formattedStr the result of the replace method on str.
How does replace work? The first parameter is a string or a RegEx.
Note: RegExps in Javascripts are Objects of type RegExp, not strings. So writing

/yourRegex/

或

New RegExp('/yourRegex/')

是等效的语法.现在让我们讨论这个特定的RegEx本身.
前导斜杠和尾部斜杠用于包围样式，末尾的g表示全局"-在第一场比赛后不要停止.
方括号描述了可以提供以匹配模式的一组字符，而+号表示该组中的1个或多个".
基本上，###将匹配，但#或 # ### # _#也会匹配，因为_和#属于同一集合.
首选行为将通过使用(#| _)+
给出这意味着#或_，一旦找到一个，就继续期待更多或所选模式".
因此___和####都会匹配，但是__ ##是2个不同的匹配组(前者是__，后者是##).
另一个问题是不知道如何用_或#替换找到的模式.
幸运的是，使用括号可以使我们使用一种称为捕获组的东西.基本上，您可以存储在临时变量中找到的任何模式，这些模式可用于替换模式.
调用它们很容易，将$附加到匹配的(模式)的位置.
例如，/(foo)textnotgetting(bar)captured(baz)/将以这种方式填充捕获组变量":

is equivalent syntax. Now let's discuss this particular RegEx itself.
The leading and trailing slashes are used to surround the pattern, and the g at the end means "globally" - do not stop after the first match.
The square parentheses describe a set of characters who can be supplied to match the pattern, while the + sign means "1 or more of this group".
Basically, ### will match, but also # or #####_# will, because _ and # belong to the same set.
A preferred behavior would be given by using (#|_)+
This means "# or _, then, once found one, keep looking forward for more or the chosen pattern".
So ___ would match, as well as #### would, but __## would be 2 distinct match groups (the former being __, the latter ##).
Another problem is not knowing wheter to replace the pattern found with a _ or a #.
Luckily, using parentheses allows us to use a thing called capturing groups. You basically can store any pattern you found in temporary variabiles, that can be used in the replace pattern.
Invoking them is easy, propend $ to the position of the matched (pattern).
/(foo)textnotgetting(bar)captured(baz)/ for example would fill the capturing groups "variables" this way:

$1 = foo
$2 = bar
$3 = baz

在我们的例子中，我们只想用第一个出现的字符替换1+个字符，并且括号中不包含+号！
所以我们可以简单地

In our case, we want to replace 1+ characters with the first occurrence only, and the + sign is not included in the parentheses!
So we can simply

str.replace("/(#|_)+/g", "$1");

为了使其正常工作.

祝你有美好的一天！

In order to make it work.

Have a nice day!

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