What is 'type inference' in TypeScript?

Q: What is 'type inference' in TypeScript?

**Default Parameters:** When a default value is assigned to a parameter, TypeScript infers its type from that value. **Contextual Typing:** TypeScript infers the types of variables based on their usage, such as in callbacks or event listener **Function Return Type:** If a function returns a value, TypeScript infers the return type based on the function body. **Variable Inference:** When you declare a variable and initialize it with a value, TypeScript infers the type from the assigned value. const numbers: number[] = [1, 2, 3]; numbers.forEach((num) => { console.log(num.toFixed(2)); }); document.addEventListener("click", (event) => { console.log(event.clientX); console.log(event.clientY); }); function add(a: number, b: number) { return a + b; } let age = 25; let name = "Gaurav"; let isActive = true; age → number let name = "Gaurav"; isActive → boolean

Difficulty: 6/10

type inference basics, generic inference, contextual typing

Type inference in TypeScript is a feature where the compiler automatically determines the type of a variable, function, or expression without the need for explicit type annotations from the developer. This enhances productivity by reducing the amount of boilerplate code, while still maintaining the benefits of static typing

1
Default Parameters: When a default value is assigned to a parameter, TypeScript infers its type from that value.
2
Contextual Typing: TypeScript infers the types of variables based on their usage, such as in callbacks or event listener
3
Function Return Type: If a function returns a value, TypeScript infers the return type based on the function body.
4
Variable Inference: When you declare a variable and initialize it with a value, TypeScript infers the type from the assigned value.

Contextual Typing

Function Return Type: TypeScript infers the return type as number.

Variable Inference

TypeScript infers the following types:

1
age → number
2
let name = "Gaurav";
3
isActive → boolean

Scenario Questions

0-2 years experience

What is 'type inference' in TypeScript?

Scenario Questions

Follow-up Questions