Lua - get indexOf string

Question

I am stuck with a problem in Lua to check whether the string value is not presented in another string.

That's how I likely will do it in Javascript:

'my string'.indexOf('no-cache') === -1 // true

but in Lua I'm trying to use string module which gives me unexpected response:

string.find('my string', 'no-cache') -- nil, that's fine but..
string.find('no-cache', 'no-cache') -- nil.. that's weird
string.find('no-cache', 'no') -- 1, 2 here it's right.. strange..

Answer 1

As has already been mentioned, - is a pattern metacharacter, specifically:

• a single character class followed by '-', which also matches 0 or more repetitions of characters in the class. Unlike '*', these repetition items will always match the shortest possible sequence;

You might be interested in the plain option for string.find. This will avoid the need for escaping anything else in the future.

string.find('no-cache', 'no-cache', 1, true)

Answer 2

- is a pattern metacharacter in lua. You need to escape it. string.find('no-cache', 'no%-cache')