What are literal types?

Q: What are literal types?

alignment: 'left' | 'right' | 'center' We can combine these with non-literal types. Numeric and Boolean literal types work the same way function printText(s: string, alignment: "left" | "right" | "center") { // ... } printText("Hello, world", "left"); printText("G'day, mate", "centre"); Argument of type '"centre"' is not assignable to parameter of type '"left" | "right" | "center"'.

Difficulty: 5/10

union types, discriminated unions, const assertions

In addition to the general types, string and number, we can refer to specific strings and numbers in type positions. By themselves, literal types aren't beneficial, It's not much use to have a variable that can only have one value! But by combining literals into unions, you can express a much more useful concept - for example, functions that only accept a certain set of known values

Example:

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alignment: 'left' | 'right' | 'center'
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We can combine these with non-literal types.
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Numeric and Boolean literal types work the same way

javascript

Scenario Questions

0-2 years experience

2-5 years experience

1You’re adding a new feature flag to a config object that can be 'enabled' or 'disabled'. The existing code uses a union of string literals for the flag. After a recent refactor, a bug appears where passing a variable with type string is accepted. Walk me through why that happened and how to fix it.

Follow-up Questions