Javascript 正则表达式检查字符串是否以 开头，忽略大小写差异

Regex to check whether string starts with, ignoring case differences

提问by Rajat Gupta

I need to check whether a word starts with a particular substring ignoring the case differences. I have been doing this check using the following regex search pattern but that does not help when there is difference in case across the strings.

我需要检查一个单词是否以特定的子字符串开头而忽略大小写差异。我一直在使用以下正则表达式搜索模式进行此检查，但是当字符串之间的大小写不同时，这无济于事。

my case sensitive way:

我区分大小写的方式：

var searchPattern = new RegExp('^' + query);
if (searchPattern.test(stringToCheck)) {}

回答by Felix Kling

Pass the imodifier as second argument:

将i修饰符作为第二个参数传递：

new RegExp('^' + query, 'i');

Have a look at the documentationfor more information.

查看文档以获取更多信息。

回答by Guffa

You don't need a regular expression at all, just compare the strings:

您根本不需要正则表达式，只需比较字符串：

if (stringToCheck.substr(0, query.length).toUpperCase() == query.toUpperCase())

Demo: http://jsfiddle.net/Guffa/AMD7V/

演示：http: //jsfiddle.net/Guffa/AMD7V/

This also handles cases where you would need to escape characters to make the RegExp solution work, for example if query="4*5?"which would always match everything otherwise.

这也处理您需要转义字符以使 RegExp 解决方案工作的情况，例如，如果query="4*5?"它总是匹配其他所有内容。

回答by grepit

I think all the previous answers are correct. Here is another example similar to SERPRO's, but the difference is that there is no new constructor:

我认为以前的所有答案都是正确的。这是另一个类似于 SERPRO 的示例，但不同之处在于没有新的构造函数：

Notice:iignores the case and ^means "starts with".

注意：i忽略大小写并^表示“开始于”。

 var whateverString = "My test String";
 var pattern = /^my/i;
 var result = pattern.test(whateverString);
 if (result === true) {
     console.log(pattern, "pattern matched!");
 } else {
     console.log(pattern, "pattern did NOT match!");
 }

Here is the jsfiddle(old version) if you would like to give it a try.

如果您想尝试一下，这里是jsfiddle（旧版本）。

回答by SERPRO

In this pageyou can see that modifiers can be added as second parameter. In your case you're are looking for 'i' (Canse insensitive)

在此页面中，您可以看到可以添加修饰符作为第二个参数。在您的情况下，您正在寻找“我”（Canse 不敏感）

//Syntax
var patt=new RegExp(pattern,modifiers);

//or more simply:

var patt=/pattern/modifiers;