Visit complete TypeScript roadmap

← Back to Topics List

Type Predicates

Type predicates are functions that return a boolean value. They are used to narrow the type of a variable. Type predicates are used in type guards.

function isString(value: unknown): value is string {
  return typeof value === 'string';

function example(x: unknown) {
  if (isString(x)) {
    // We can now call any 'string' method on 'x'.
  } else {

Learn more from the following links:

Community is the 6th most starred project on GitHub and is visited by hundreds of thousands of developers every month.

Roadmaps Best Practices Guides Videos Store YouTube by Kamran Ahmed

Community created roadmaps, articles, resources and journeys to help you choose your path and grow in your career.

© · FAQs · Terms · Privacy


The leading DevOps resource for Kubernetes, cloud-native computing, and the latest in at-scale development, deployment, and management.