JavaScript: Is String containing another String?

In JavaScript, the function contains() in relation to strings can not be used in this way. You need the function indexOf(), which you can use something like this:

var str = "ABCDEF";
 
if (str.indexOf("CDE") != -1) {
   alert('The string contains "CDE".');
} else {
   alert('The string does not contain "CDE".');
}

As a parameter, you pass the string, you would like to search for. In the example above, this is "CDE". The function then gives us the position of the passed string, or -1, if there is no position, so therefore, the string is not included.

In our example, "CDE" is included in "ABCDEF". This would make the IF condition not -1 and 'The string contains "CDE".' would be the alert.

Important: Make sure, that you also write "indexOf" and not "indexof". Otherwise it is not working.
Last update on 2021-01-13 | Created on 2012-08-07