# Typescript - Tips & Tricks - Tuple

> Tuple types allow you to express an array with a fixed number of elements whose types are known, but...

- **Author**: Luca Del Puppo (@puppo92) — AI Native Engineer at Nearform
- **Published**: Mar 12, 2021
- **Canonical URL**: https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-tuple/
- **Series**: TypeScript - Tips & Tricks (Part 12 of 21) — https://delpuppo.net/blog/series/ts-tips-and-tricks/
- **Series LLMs.txt**: https://delpuppo.net/blog/series/ts-tips-and-tricks/llms.txt
- **Category**: TypeScript
- **Tags**: typescript, webdev
- **Hashnode Mirror**: https://blog.delpuppo.net/typescript-tips-tricks-tuple
- **Dev.to Mirror**: https://dev.to/playfulprogramming/typescript-tips-tricks-tuple-3ep7
- **Blog Index LLMs.txt**: https://delpuppo.net/blog/llms.txt

## Series Context: TypeScript - Tips & Tricks

- Part 1: [Typescript - Tips & Tricks - typeof](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-typeof/)
- Part 2: [Typescript - Tips & Tricks - Literal Types](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-literal-types/)
- Part 3: [Typescript - Tips & Tricks - keyof](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-keyof/)
- Part 4: [Typescript - Tips & Tricks - Union and Intersection](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-union-and-intersection/)
- Part 5: [Typescript - Tips & Tricks - Overloaded Functions](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-overloaded-functions/)
- Part 6: [Typescript - Tips & Tricks - this parameter](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-this-parameter/)
- Part 7: [Typescript - Tips & Tricks - any vs. unknown](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-any-vs-unknown/)
- Part 8: [Typescript - Tips & Tricks - Optional modifier](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-optional-modifier/)
- Part 9: [Typescript - Tips & Tricks - Index Signature](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-index-signature/)
- Part 10: [Typescript - Tips & Tricks - readonly modifier](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-readonly-modifier/)
- Part 11: [Typescript - Tips & Tricks - Readonly Array](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-readonly-array/)
- Part 12: [Typescript - Tips & Tricks - Tuple](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-tuple/) **(Current Article)**
- Part 13: [Typescript - Tips & Tricks - Non-null assertion operator](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-non-null-assertion-operator/)
- Part 14: [Typescript - Tips & Tricks - Never type](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-never-type/)
- Part 15: [Typescript - Tips & Tricks - Assert Function](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-assert-function/)
- Part 16: [Typescript - Tips & Tricks - Type Guard](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-type-guard/)
- Part 17: [Typescript - Tips & Tricks - Conditional Type](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-conditional-type/)
- Part 18: [Typescript - Tips & Tricks - infer keyword](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-infer-keyword/)
- Part 19: [Typescript - Tips & Tricks - Mapped Types](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-mapped-types/)
- Part 20: [Typescript - Tips & Tricks - Advanced Types](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-advanced-types/)
- Part 21: [Typescript - Tips & Tricks - Rest Parameters & Rest Arguments](https://delpuppo.net/blog/ts-tips-and-tricks/typescript-tips-tricks-rest-parameters-rest-arguments/)

---

Tuple types allow you to express an array with a fixed number of elements whose types are known, but need not be the same.
This definition is picking from the typescript documentation.
The tuple type is a powerful type that helps you to identify the types of elements in an array, you can create special types where the elements of the array can have different types.
A simple example
```ts
type Point = [number, number];

const point1: Point = [10, 10];
const point2: Point = [10, "10"]; // Type 'string' is not assignable to type 'number'
const point3: Point = [10, 10, 20]; // Type '[number, number, number]' is not assignable to type 'Point'. Source has 3 element(s) but target allows only 2.
```
In this case, you can see how the point type is composed by a fixed array of two elements of type number. You can see how typescript detects this constraint and it raises an error when you try to create a point with the second element of type string or you try to create a point with 3 elements.
To show you the power of this type, here's another example
```ts
type QueryStringItem = [string, number | string | boolean];
const queryStringItem1: QueryStringItem = ["key1", 10];
const queryStringItem2: QueryStringItem = ["key2", "value2"];
const queryStringItem3: QueryStringItem = ["key3", false];
const queryStringItem4: QueryStringItem = ["key3", { value: "value" }]; // Type '{ value: string; }' is not assignable to type 'string | number | boolean'.
```
In this case, you can see how the second element of the Tuple can be a [union type](https://dev.to/puppo/typescript-tips-tricks-union-and-intersection-1a9l) of the types: number, string, or boolean; so typescript let you set the second element of the Tuple with one of these last three types. If you try to set the second element with a different type from number, string or boolean the typescript compiler raises an error.

That's all from the Tuple type.
See you soon guys!