How to Use Optional Chaining in JavaScript

How to Use Optional Chaining in JavaScript

Ferenc Almasi β€’ 2020 August 05 β€’ πŸ“– 1 min read

Optional chaining is coming to JavaScript. It lets you access deeply nested properties without having to explicitly check each object for its existence.

Instead of getting the famous β€œcannot read property of undefined” error message, the expression short circuits with undefined.

To use it, simply mark optional properties with a question mark:

// If `dateOfBirth` is undefined, `birthYear` will be undefined as well
const birthYear = user.dateOfBirth?.year;
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For full browser support, make sure you check the compatibility table on MDN.

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Do You Need a Fallback Option?

If you rather want to use a more compatible version, you can achieve the same thing using a reduce function.

const getProperty = (obj, path) => (path.split('.').reduce((value, el) => value[el], obj));

const user = {
  settings: {
    theme: 'default'

getProperty(user, 'settings.theme');       // This will return β€œdefault”
getProperty(user, 'settings.invalidPath'); // This will return `undefined`
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How to Use Optional Chaining in JavaScript
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