Understanding Array and Tuples
The Array type is used to store same type of multiple values in a single variable and further your array elements you can access using the index number.
An Array type can be defined using square brackets '[ ]' followed by elemType or generic array type 'Array
array.ts
let numberList: number[] = [1, 2, 3]; //OR let numList: Array= [1, 2, 3];
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
array.js
var numberList = [1, 2, 3]; var numList = [1, 2, 3];
Tuple
The Tuple type represents a JavaScript array where you can define the datatype of each element in array.
tuple.ts
let tuple: [string, number]; tuple = ["Gurukulsight", 1];
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
tuple.js
var tuple; tuple = ["Gurukulsight", 1];
Type Annotation
Type Annotations means defining the type of a variable explicitly. The type used to specify an annotation can be a primitive type, an object type or any complex structure to represent data.
The type of a variable is defined by using colon (:) followed by type.
Syntax
: = ; : ;
type_annotation.ts
let num: number = 2; //type of num is number let str: string = "Gurukulsight"; //type of str is string let numberList: number[] = [1, 2, 3]; //type of numberList is number array
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
type_annotation.js
var num = 2; var str = "Gurukulsight"; var numberList = [1, 2, 3];
Type Inference
Type inference is a mechanism to determine the type of data at compile time in the absence of explicit type annotations. TypeScript will infer the type from the initial value.
type_inference.ts
let myString = 'Hello Gurukulsight'; // string let myBool = true; // boolean let myNumber = 1.23; // number let myArray = ['Hello', 'Gurukulsight']; // string[]
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
type_inference.js
var myString = 'Hello Gurukulsight'; // string var myBool = true; // boolean var myNumber = 1.23; // number var myArray = ['Hello', 'Gurukulsight']; // string[]
Type Assertion
A type assertion is just like a type casting, but it doesn’t perform special type checking or restructuring of data just like other languages like C# and Java. This process entirely works on compile time. Hence it has no impact on runtime.
Type assertions can be done using two ways
1. Angle-bracket syntax
anglebracket.ts
let anyValue: any = "Welcome to www.gurukulsight.com!"; let strLength: number = (anyValue).length;
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
anglebracket.js
var anyValue = "Welcome to www.gurukulsight.com!"; var strLength = anyValue.length;
2. As syntax
anglebracket.ts
let anyValue: any = "Welcome to www.gurukulsight.com!"; let strLength: number = (anyValue).length;
The compiled JavaScript (ES5) code for the above TypeScript code is give below:
anglebracket.js
var anyValue = "Welcome to www.gurukulsight.com!"; var strLength = anyValue.length;
What do you think?
I hope you will enjoy the Object and Miscellaneous Data Type in TypeScript while developing your web app. I would like to have feedback from my blog readers. Your valuable feedback, question, or comments about this article are always welcome.
