How to use Union types In JavaScript
The union type can be used to specify the multiple types for the values of a key in TypeScript dictionary. Different types will be seprated using the straight line (|).
Syntax:
type dictionaryName = {
key: typesSeparatedUsingStraightLine;
}
Example: The below code will explain the way of defining the dictionaries with multiple type values.
Javascript
type myDictionary = { [key: string]: number | string | boolean;}const dictionaryObj1: myDictionary = { name: "w3wiki", desc: "A Computer Science Portal", workForce: 200}const dictionaryObj2: myDictionary = { isw3wiki: true,}if (dictionaryObj2.isw3wiki) { console.log( `Company Name: ${dictionaryObj1.name} Description: ${dictionaryObj1.desc} Workforce: ${dictionaryObj1.workForce}+`);} |
Output:
Company Name: w3wiki
Description: A Computer Science Portal
Workforce: 200+
How to Extend the Possible Types of Values of Dictionary in TypeScript ?
A dictionary in TypeScript is a data type that can store the data in the form of key-value pairs. The dictionaries in TypeScript can be created using the type keyword, Interfaces, or simple objects. The type of the values in a dictionary can be predefined in TypeScript which can be extended to store values of different kinds. Let us discuss different ways to extend possible types of values of the dictionary.
Table of Content
- Using Generics
- Using Union types
- By mapping types
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