While you will generally be advised to not parse HTML with regular expressions (see my all-time favorite S.O. answer), you can approximate it with something like:
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"<script.*?>(.*?)</script>"
options:NSRegularExpressionCaseInsensitive | NSRegularExpressionDotMatchesLineSeparators
error:&error];
[regex enumerateMatchesInString:string
options:0
range:NSMakeRange(0, [string length])
usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
NSLog(@"%@", [string substringWithRange:[result rangeAtIndex:1]]);
}];