The indexOf () method is case-sensitive and accepts two parameters. What counts as a string in this case? Hence, we can still implement the same basic algorithm but using a much quicker array lookup rather than an object lookup. The following article describes how to check for whether a string contains string in PHP, or simply said how to find string within string in PHP. Thank you :) lamdan. The most common method: string.indexOf() string.indexOf() How do I include a JavaScript file in another JavaScript file? if we have eee, we will replace it with a single e. If you're searching for character(s) in the start or at the end of the string, you can also use startsWith and endsWith const country = "pakista The following example defines two string variables. We can check whether a string contains all unique characters by following these steps-Traverse the string from starting character by character. There are a lot of people who don't understand regex, and generally the simpler answer is the best. Recommended: Please solve it on PRACTICE first, before moving on to the solution. I just made a slighty different variant with every and includes , jsperf says that there's a litte bit difference on performance (the code bel alert("hello found inside your_string"); // Validation failed