regexp只允许在单词之间留一个空格 [英] regexp to 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) test[space]ing - Should be allowed 
2) testing - Should be allowed 
3) [space]testing - Should not be allowed 
4) testing[space] - Should be allowed but have to trim it 
5) testing[space][space] - should be allowed but have to trim it 

只允许一个空格。可能吗？

Only one space should be allowed. Is it possible?

推荐答案

function validate(s) {
    if (/^(\w+\s?)*\s*$/.test(s)) {
        return s.replace(/\s+$/, '');
    }
    return 'NOT ALLOWED';
}
validate('test ing')    // => 'test ing'
validate('testing')     // => 'testing'
validate(' testing')    // => 'NOT ALLOWED'
validate('testing ')    // => 'testing'
validate('testing  ')   // => 'testing'
validate('test ing  ')  // => 'test ing'

BTW，新的RegExp（..）是多余的。

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