Regex to check whether string starts with, ignoring case differences

Question

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.

my case sensitive way:

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

Answer 1

Pass the i modifier as second argument:

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

Have a look at the documentation for more information.

Answer 2

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

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

Demo: 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.