Expression selector

The expression selector is the most versatile, as it allows you to use any expression to access a property or an item in a list.

This selector is especially useful when the property name is not a valid identifier or when you want to dynamically compute the index or key.

For example, say you want to get the value of a query string parameter named referral code. Because the property name contains spaces, you can only access it using the expression selector:

page.query['referral code']

Because you can use any expression, you could store the property name in a variable and use it in the expression:

let param = 'referral code';

page.query[param]

You can also use numeric indexes to access items in a list:

let transport = ["🚀", "🚗", "🚆"];

transport[0] // 🚀

Notice that the index is zero-based, so the first item has an index of 0, the second item has an index of 1, and so on. For a more natural way to access items in a list, see the ordinal selector.