“？ ' - 正则表达式 - js [英] '? ' - Regular expression - js

问题描述

let american = "color";
let rainbowRegex= /colou?r/;
rainbowRegex.test(american); // Returns true -- why?

我尝试过：



了解并尝试另一个例子。但仍然，我什么都不懂

What I have tried:

to understand and try another examples. but still, i understand nothing

推荐答案

因为'？'就在它自己的前面（前面没有'*'或'+'）说零或一上一个元素。

所以colou？r匹配颜色或颜色而不是colotr。



正如我上次建议的那样，获取 Expresso 的副本[ ^ ] - 它是免费的，它检查并生成正则表达式。

它会向你解释这个！

Because '?' on it's own (without '*' or '+' in front of it) says "zero or one" of the preceding element.
So "colou?r" matches either "color" or "colour" but not "colotr".

As I suggested last time, get a copy of Expresso[^] - it's free, and it examines and generates Regular expressions.
It would have explained this to you!

你在正则表达式中是可选的，如？



所以'颜色'和'颜色'都是将匹配。



键入colou？进入正则表达式框，在这里查看：



< a href =https://www.debuggex.com/> Debuggex：在线可视正则表达式测试器。 JavaScript，Python和PCRE。 [ ^ ]

The u is optional in the regex, as denoted by the ?

So both 'color' and 'colour' will match.

Type colou?r in to the regex box on here to see:

Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]

Quote：

'？ ' - 正则表达式 - js

'? ' - Regular expression - js

建议：阅读文档。



以下是RegEx文档的链接：

perlre - perldoc.perl.org [ ^ ]

以下是帮助构建RegEx并调试它们的工具的链接：

.NET正则表达式测试程序 - 正则表达式风暴 [ ^ ]

Expresso正则表达式工具 [ ^ ]

RegExr：Learn，Build，&测试RegEx [ ^ ]

在线正则表达式测试器和调试器：PHP，PCRE，Python，Golang和JavaScript [ ^ ]

这个显示RegEx是一个很好的图表，它非常有助于理解RegEx的作用： Debuggex：在线可视正则表达式测试器。 JavaScript，Python和PCRE。 [ ^ ]

此网站还在一个漂亮的图表中显示正则表达式，但无法测试与RegEx匹配的内容： Regexper [ ^ ]

Advice: read documentation.

Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
RegExr: Learn, Build, & Test RegEx[^]
Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx: Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
This site also show the Regex in a nice graph but can't test what match the RegEx: Regexper[^]

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