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test and match

JavaScript course · Intermediate · Lesson 121/134

Learn to check a match with test and extract matches with match.

The .test() method

The .test() method of a RegExp returns true when the pattern matches the string and false otherwise. The result is always a boolean.

const re = /\d/;
re.test("abc5"); // true
re.test("abc");  // false

When you only need to ask "does this text match this pattern?", test is the fastest way. Use it when you do not need to extract the matched part.

The .match() method

The .match() method of a string extracts the matched part. It returns null when there is no match, and an array when there is. The first item of the array is the full match.

"date 2024".match(/\d+/);
// ["2024", ...]

Add the g flag and you get an array of all matches. This lets you pull every number, code or tag out of a text in one call.

Exercise Extract the first word

Assign the first matching word to firstWord using sentence.match(). Use \w+ for the word pattern. Then log firstWord[0] with console.log.

Show example solution 
The match method takes a regex and returns the match as an array. Use \w+ for a word.
Example solution:
let firstWord = sentence.match(/\w+/);
console.log(firstWord[0]);

Test yourself

  1. What does the .test() method of a RegExp return?

    • a string
    • a boolean (true/false)
    • a number
    • an array
    Show answer

    a boolean (true/false) — Correct! .test() always returns true or false.

  2. Call the test method

    const re = /\d/;
const found = re.____("abc5");
console.log(found);
    Show answer 
    const re = /\d/;
const found = re.test(("abc5");
console.log(found);

  3. Match methods with their result

    .test()
    true/false
    .match()
    first match
    .exec()
    next match
    /g flag
    finds all

All lessons in Intermediate

1 Arrow functions

  1. Arrow function syntax
  2. Single-line and block body
  3. Parameters with arrows
  4. The this context
  5. Arrow vs function
  6. Summary - Arrow functions

2 Scope

  1. Global scope
  2. Function scope
  3. Block scope
  4. Variable shadowing
  5. Hoisting
  6. Summary - Scope

3 Closures

  1. What is a closure?
  2. Factory functions
  3. Immediately Invoked Function Expressions
  4. The module pattern
  5. Closure pitfalls
  6. Summary - Closures

4 DOM basics

  1. What is the DOM?
  2. getElementById
  3. querySelector
  4. querySelectorAll
  5. textContent and innerText
  6. Summary - DOM basics

5 DOM manipulation

  1. Creating elements with createElement
  2. appendChild and removeChild
  3. The classList API
  4. setAttribute and removeAttribute
  5. innerHTML and insertAdjacentHTML
  6. Summary - DOM manipulation

6 Events

  1. addEventListener basics
  2. Click events
  3. Mouse events
  4. Keyboard events
  5. The event object
  6. Summary - Events

7 Event handling

  1. Event bubbling
  2. stopPropagation
  3. Event delegation
  4. preventDefault
  5. once and passive options
  6. Summary - Event handling

8 Local storage

  1. localStorage basics
  2. sessionStorage
  3. Storing data with JSON
  4. Clearing storage
  5. Storage events
  6. Summary - Local storage

9 Project: To-do app

  1. Project: To-do app
  2. UI skeleton
  3. Adding a task
  4. Completing and deleting a task - DOM
  5. Project final - To-do DOM

10 Forms

  1. Accessing form elements
  2. Reading input values
  3. The form submit event
  4. Basic validation
  5. Checkbox and radio
  6. Summary - Forms

11 Timers

  1. setTimeout
  2. setInterval
  3. Stopping with clearInterval
  4. requestAnimationFrame
  5. Timer cleanup
  6. Summary - Timers

12 Callbacks

  1. Callback functions
  2. Asynchronous callbacks
  3. Error-first callbacks
  4. Callback hell
  5. Managing callbacks
  6. Summary - Callbacks

13 Promises

  1. What is a promise?
  2. Catching success with then
  3. Catching errors with catch
  4. Cleanup with finally
  5. Promise.all and Promise.race
  6. Summary - Promises

14 async/await

  1. async functions
  2. The await operator
  3. Async error handling
  4. Parallel await
  5. await expressions
  6. Summary - async/await

15 Fetch API

  1. fetch basics
  2. Reading JSON
  3. HTTP headers
  4. POST requests
  5. HTTP error handling
  6. Summary - Fetch API

16 Project: Weather panel

  1. Project: Weather panel
  2. UI and city input
  3. Fetching data with fetch
  4. Rendering data to the DOM
  5. Project final - Weather panel

17 Project: Gallery app

  1. Project: Gallery app
  2. Fetching the image list
  3. Building the gallery grid
  4. Large image view
  5. Project final - Gallery

18 Error handling

  1. Custom error classes
  2. Error propagation
  3. Multiple catch patterns
  4. Async error strategies
  5. Global error handling
  6. Summary - Error handling

19 JSON

  1. The JSON format
  2. JSON.parse
  3. JSON.stringify
  4. structuredClone
  5. JSON limitations
  6. Summary - JSON

20 Date and time

  1. Creating Date objects
  2. Reading date components
  3. Formatting dates
  4. Intl.DateTimeFormat
  5. Date arithmetic
  6. Summary - Date and time

21 RegExp basics

  1. RegExp syntax
  2. Character classes
  3. Quantifiers
  4. test and match
  5. replace and split with regex
  6. Summary - RegExp basics

22 Modules

  1. What is a module?
  2. Named export
  3. Default export
  4. The import statement
  5. Module vs script
  6. Summary - Modules

23 Intermediate final

  1. Challenge - DOM app
  2. Challenge - Async flow
  3. Challenge - Form and storage
  4. Challenge - Timers and animation
  5. Challenge - Modular structure