See the tutorial on JavaScript ES6 Features to learn more about arrow function notation. A case-insensitive comparison is done by converting the two strings to the same case. The some() method is supported in all major browsers, such as Chrome, Firefox, IE (9 and above), etc. Perform a case-insensitive check if a string is in an array using filter () Make includes () case insensitive in JavaScript To make the String.includes () method case insensitive, convert both of the strings in the comparison to lowercase. Likewise, two distinct arrays are not equal even if they have the same values in the same order. Because, two distinct objects are not equal even if they look the same (i.e. Var persons = [) it will not work (always return -1). indexOf ( 'nice', 3 ) != - 1 //false 'a nice string'. indexOf ( 'nice' ) != - 1 //true 'a nice string'. Like includes(), the second parameters sets the starting point: 'a nice string'.

If the substring is found, it returns the index of the character that starts the string. Pre-ES6, the common way to check if a string contains a substring was to use indexOf, which is a string method that return -1 if the string does not contain the substring. The includes method will return true if the value is contained in the array and false otherwise. includes ( 'nice', 2 ) //true Pre-ES6 alternative to includes(): indexOf() Check if an Object is contained in an Array in TypeScript Check if an Array contains a Value in TypeScript Use the includes () method to check if an array contains a value in TypeScript. includes ( 'nice', 3 ) //false 'a nice string'. includes ( 'nice' ) //true 'a nice string'. Includes() also accepts an optional second parameter, an integer which indicates the position where to start searching for: 'a nice string'. To use it on all browsers, use Polyfill.io or another dedicated polyfill. It’s supported in all modern browsers except Internet Explorer: This method was introduced in ES6/ES2015. The most simple one, and also the canonical one going forward, is using the includes() method on a string: 'a nice string'. JavaScript offers different ways to perform this operation. Learn the canonical way, and also find out all the options you have, using plain JavaScriptĬhecking if a string contains a substring is one of the most common tasks in any programming language. includes () to see if an array includes an item unless your array has more than 100,000 items. JavaScript offers many ways to check if a string contains a substring.

Typescript includes