TypeScript adds syntax to JavaScript to allow for tighter integration with your editor. Make sure to catch errors in your editor as soon as possible. TypeScript code can be converted to JavaScript and runs wherever JavaScript runs: in a browser, on Node.js, Deno, or in your apps. TypeScript can understand JavaScript and uses type-inference to provide great tooling for JavaScript without any additional code. 78% of 2020 State of JS respondents used TypeScript, and 93% said they would use it again. Type errors are the most common errors programmers make. A certain type of value was used when a different value was expected. This could be simple typos, failure to understand an API surface, incorrect assumptions about runtime behavior or other errors.