RegExp，只允许在单词之间留一个空格 [英] RegExp which allow only one space in between words

问题描述

我正在尝试编写一个正则表达式来从单词的开头删除空格，而不是在单词后面的单个空格中删除空格。

I'm trying to write a regular expression to remove white spaces from just the beginning of the word, not after, and only a single space after the word.

使用RegExp：

var re = new RegExp(/^([a-zA-Z0-9]+\s?)*$/);

测试Exapmle：

1) wordX[space] - Should be allowed 
2) [space] - Should not be allowed 
3) WrodX[space][space]wordX - Should be allowed 
4) WrodX[space][space][space]wordX - Should be allowed 
5) WrodX[space][space][space][space] - Should be not be allowed 
6) WrodX[space][space] - Allowed with only one space the moment another space is entered **should not be allowed** 

推荐答案

试试这个：

^\s*\w+(\s?$|\s{2,}\w+)+

测试用例（为了清晰起见，添加了）：

Test cases ("s added for clarity):

"word"         - allowed (match==true)
"word "        - allowed (match==true)
"word  word"   - allowed (match==true)
"word   word"  - allowed (match==true)
" "            - not allowed (match==false)
"word  "       - not allowed (match==false)
"word    "     - not allowed (match==false)
" word"        - allowed (match==true)
"  word"       - allowed (match==true)
"  word "      - allowed (match==true)
"  word  word" - allowed (match==true)

在此处查看演示。

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