Typescript is a superset of JavaScript which primarily provides optional static typing, classes, and interfaces. We have written some Refined interview questions on Typescript that helps developers to crack interview on TypeScript.
Below are the list of some Typescript Interview Questions and their Answers that may be asked by an interviewer in your interview
| Typescript is | subset of Javascript. |
| Typescript is Licensed under | Apache License 2.0 |
| Typescript is Designed by | Microsoft Corporation |
| Typescript file extension | ts,.tsx |
| Typescript is released | on 1 October 2012 |
| Typescript is | based on Duck, gradual, structural typing discipline |
Below are the list of Best Typescript Interview Questions and Answers
Differences between Typescript and JavaScript are
Generics are a kind of tool which is consists of the ability to abstract types. It is used in TypeScript to create reusable code components that work with a varied range of types instead of a single type.
The Most popular Features of Typescript are:-
These are also called the primitive types in Typescript. These are of 5 types: –
Syntax- var variable_name: number;
Syntax- var variable_name: string;
Syntax- var variable_name: bool;
Syntax- var variable_name:number=null;
Syntax- var variable_name:number=undefined;
Modules are executed within their own scope, not in the global scope; this means that variables, functions, classes, etc. declared in a module are not visible outside the module unless they are explicitly exported using one of the export forms.
Creating a Module
module module_name{
class xyz{
export foo(x, y){
return x*y;
}
}
}
Installing Typescript with the help of node and npm is recommended. Here, npm is used to install all the libraries and tools. The typescript should be installed globally using
npm install –g typescript
It installs a command line code “tsc” which will further be used to compile your Typescript code. Make sure that you check the version of Typescript installed on your system.
The following steps are involved in installing Typescript on your system:
npm install –g typescript
You should always keep in mind, that a variable should be declared before being used. Variables in Typescript are declared by placing a “var” keyword prior to the variable name. A variable can be declared using 4 methods: –
Syntax-
interface interface_name{
Statements;
}
Interfaces need not to be converted to JavaScript for execution. They have zero runtime JavaScript impact. Interfaces can define both the kind of keys which an array uses and the type of entry it contains.
class Greeter {
greeting: string;
constructor (message: string) {
this.greeting = message;
}
greet() {
return "Hello, " + this.greeting;
}
}
Some features of a class are-
tsc --outFile outputfile.ts file1.ts file2.ts file3.ts ... filen.ts
Closures are nothing but a statefull functions.
A closure is an inner function that has access to outer function’s variables in addition to it’s own variable and global variables.In simple term a closure is a function inside a function.Closures using Lexical scoping in which function have access to global and outer variables.Below is a sample example of Javascript closure.
function employee() {
var employee_dept = 'IT';
return {
getDept: function () {
return employee_dept;
},
setDept: function (new_dept) {
employee_dept = new_name;
}
}
}
var emp1 = employee (); // In this juncture, the employee_dept outer function has returned.
mjID.getDept(); // IT
mjID.setDept('Account'); // Changes the outer function's variable
mjID.getDept(); //outputs Account
Closures prevents your important variable to be modified accidently.It can be only modified by itself.
namespace YourNameSpace {
export class Class1 { }
export class Class2 { }
}
Decorators are function that supports annotating or modifying classes its members.Its allow way to add both annotations and a meta-programming syntax for class declarations and members. Decorators are an experimental feature of Typescript and maybe change in future releases.
You can enable Decorators using the command line or editing your tsconfig.json
Enabling Decorators in TypeScript via command line
tsc --target ES5 --experimentalDecorators
Type assertion allows you to set the type of a value. After the value set, typescript told the compiler not to assume the type of value.
The classes in TypeScript must follow the structure of the interface. The interface contains the method declaration, variable declaration.
The optional properties use as an optional thing. The interface typescript has many properties but every property not required. You can pass the object into interface using ( ? ) question mark symbol.
A module is used to create a set of related variables, functions, classes, and interfaces, etc in the Typescript. The internal and external module has two categories of Typescript.
Duck-typing used to check the type compatibility for more complex variable types in typescript. This method checks the type matching between two objects. If the property contains more or less or not match then a compile-time error occurred.
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