How to useMapped Types in Typescript
By changing existing types, mapped types make it possible to create new ones. We can create a type with certain value types while keeping the keys accessible by utilizing mapped types.
Syntax:
type MyObject = { [key: string]: ValueType };
Example: This example shows the declaration of the object value type without declaring the key type by the use of the mapped type.
Javascript
// Approach 2: Leveraging Mapped Types in JavaScript// Indexed type with string keystype StringIndexedType = { // Value type for string keys [key: string]: number;};// Indexed type with number keystype NumberIndexedType = { // Value type for number keys [key: number]: string;};// Example usageconst stringIndexedObject: StringIndexedType = { "key1": 10, "key2": 20,};const numberIndexedObject: NumberIndexedType = { 1: "value1", 2: "value2",};// Output using console.logconsole.log(stringIndexedObject["key1"]);console.log(numberIndexedObject[1]); |
Output:
10
value1
How to Declare Object Value Type Without Declaring Key Type in TypeScript ?
We will create an object value type without declaring the key type. We can not directly define the type of value we will use different methods for declaring the object value type.
These are the following methods for declaring the object value type:
Table of Content
- Using Record Utility Type
- Using Mapped Types
- Using Generics
- By utilizing Indexed Types
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