IndexOf does a case-sensitive search on the string. var string = 'foo' var substring = 'oo' console.log(string.indexOf(substring) != -1) // true It is often used in arrays, and the same can be applied with strings. The indexOf method would return -1 if the substring is not present in the string. IndexOf can be used to decide if the string, contains a substring or not.

This means, you must have a fallback mechanism in your code to handle these environments. Older browsers, and especially Internet Explorer does not support. Includes does a case-sensitive search on the string.Īs developers, you need to be watchful off when the includes is being used. const str = 'Bread and Milk' Ī captivating guide to the subtle caveats and lesser-known parts of JavaScript.If you are using the most recent version of JavaScript, for development, you have the liberty of using the includes function in the String Prototype.ĮCMAScript 6 introduced const string = 'foo' const substring = 'oo' console.log(string.includes(substring)) // true Using regex matching allows us to specify multiple characters to search for in the string easily. It returns true if it finds a match, and false otherwise. The test() method searches the string for a match with the regex. One way to do this is with the RegExp test() method. We can test the string against regex patterns to determine if it contains a particular character. This is why we compare the result of indexOf() with -1 to check if the character is in the string. If the value can’t be found, it returns -1. The indexOf() method searches a string for a value and returns the index of the first occurrence of that value. For example: const str = 'Bread and Milk' Ĭonsole.log(str.indexOf(char1) > -1) // trueĬonsole.log(str.indexOf(char2) > -1) // false

We call the indexOf() method on the string, passing the character as an argument. We can also use the indexOf() method to check if a string contains a particular character. const str = 'Bread and Milk' Ĭonsole.log(str.toLowerCase().includes(char.toLowerCase())) // true To perform a case-insensitive check, convert both the string and the character to lowercase before calling includes() on the string.

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