JavaScript - How To Check Whether a String Contains a Substring? Last Updated : 02 Dec, 2024 Summarize Comments Improve Suggest changes Share Like Article Like Report Here are the different methods to check whether a string contains a substring in JavaScript.1. Using includes() MethodThe includes() method is the most simple and modern way to check if a string contains a specific substring. It returns true if the substring is found within the string, and false otherwise. JavaScript let s = "JavaScript is awesome!"; let res = s.includes("awesome"); console.log(res); Outputtrue includes() checks if the substring ("awesome") exists within the string ("JavaScript is awesome!").It returns a boolean value (true or false).This method is case-sensitive, so "awesome" is different from "Awesome".2. Using indexOf() MethodThe indexOf() method searches for a substring within a string and returns the index of the first occurrence. If the substring is not found, it returns -1. JavaScript let s = "JavaScript is awesome!"; let res = s.indexOf("awesome") !== -1; console.log(res); Outputtrue indexOf() returns the index of the first occurrence of the substring.If the substring is found, the result will be an index (>= 0), otherwise -1.You can compare the result to -1 to check if the substring is present.3. Using Regular Expressions (RegExp)You can also use regular expressions to check if a substring exists within a string. This is especially useful when you want to perform case-insensitive checks or match more complex patterns. JavaScript let s = "JavaScript is awesome!"; let res = /awesome/i.test(s); console.log(res); Outputtrue /awesome/i.test(str) creates a regular expression to check if the word "awesome" exists in the string, ignoring case (i flag).The test() method returns a boolean (true or false).Regular expressions are more powerful but can be overkill for simple substring checks.4. Using search() MethodThe search() method allows you to search for a substring or regular expression pattern within a string. It returns the index of the first match or -1 if no match is found. JavaScript let s = "JavaScript is awesome!"; let res = s.search("awesome") !== -1; console.log(res); Outputtrue search() works similarly to indexOf() but can accept regular expressions.If the substring is found, it returns the index, otherwise -1.Like indexOf(), you compare the result to -1 to check for the substring.5. Using split() MethodThe split() method splits a string into an array of substrings based on a separator. You can use it to check if the string can be split into an array that includes the substring. JavaScript let s = "JavaScript is awesome!"; let res = s.split("awesome").length > 1; console.log(res); Outputtrue split("awesome") divides the string at each occurrence of "awesome".If the substring exists, the resulting array will have more than one element, and the length will be greater than 1.This method can be useful for checking multiple substrings at once.Which Approach to Choose in Which Case?MethodWhen to UseWhy Choose Itincludes()When you need a simple and modern way to check for a substring.Clean, easy-to-read syntax and good for most use cases.indexOf()When you need the index of the first occurrence of a substring.Useful for finding the position of the substring or checking existence.RegExpWhen you need more complex patterns or case-insensitive searches.Great for pattern matching and flexible, powerful checks.search()When working with regular expressions or need the index.Similar to indexOf() but allows for regular expression matching.split()When you want to check the existence of multiple substrings or split at a specific pattern.Useful for checking multiple substrings or patterns in one go. Comment More infoAdvertise with us Next Article How to check if a String Contains a Substring in PHP ? S souravsharma098 Follow Improve Article Tags : JavaScript Web Technologies javascript-string Similar Reads How to check if a String Contains a Substring in PHP ? Checking whether a string contains a specific substring is a common task in PHP. Whether you're parsing user input, filtering content, or building search functionality, substring checking plays a crucial role.MethodsBelow are the following methods by which we can check if a string contains a substri 1 min read Check If An Array of Strings Contains a Substring in JavaScript Here are the different ways to check if an array of strings contains a substring in JavaScript1. Using includes() and filter() methodWe will create an array of strings, then use includes() and filter() methods to check whether the array elements contain a sub-string.JavaScriptconst a = ['Geeks', 'gf 4 min read How to check a string is entirely made up of the same substring in JavaScript ? We are given a string and the task is to determine whether the string is made up of the same substrings or not. 1. Using Regular Expression with test() method Initialize a string to the variable.Use the test() method to test a pattern in a string.The test() method returns true if the match is found, 3 min read Javascript Program To Check If A String Is Substring Of Another Given two strings s1 and s2, find if s1 is a substring of s2. If yes, return the index of the first occurrence, else return -1. Examples :Â Input: s1 = "for", s2 = "geeksforgeeks" Output: 5 Explanation: String "for" is present as a substring of s2. 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