How to Safely Access Deeply Nested Properties in JavaScript

You can use the function below to get nested properties from objects error safe. If a property doesn’t exist, it won’t throw the famous last words: “cannot read property of undefined”

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

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

getProperty(user, 'settings.theme');       // This will return “default”
getProperty(user, 'settings.invalidPath'); // This will return `undefined`

Keep in mind that this will return undefined if the property does not exist. If your properties can be undefined on purpose and you are specifically looking for that, you may run into issues.

If you are using Babel, you can also achieve the same thing by using the optional chaining plugin.

// If `dateOfBirth` is undefined, `birthYear` will be undefined as well
const birthYear = user.dateOfBirth?.year;

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Resource

• Array.prototype.reduce method in JavaScript
• Optional chaining plugin for Babel