Quick Answer: What is rest operator in JavaScript?

What is rest and spread operator in JavaScript?

The rest operator (…) allows us to call a function with any number of arguments and then access those excess arguments as an array. … The spread operator (…) allows us to expand an iterable like array into its individual elements.

What is the purpose of the rest operator?

Summary. The spread operator allows us to spread the value of an array (or any iterable) across zero or more arguments in a function or elements in an array (or any iterable). The rest parameter allows us to pass an indefinite number of parameters to a function and access them in an array.

Which is used for rest parameter?

The last parameter ( args ) is prefixed with the three-dots ( … ). It’s called a rest parameter ( … args ).

What is difference between spread and rest operator?

The main difference between rest and spread is that the rest operator puts the rest of some specific user-supplied values into a JavaScript array. But the spread syntax expands iterables into individual elements.

What is rest API services?

A REST API (also known as RESTful API) is an application programming interface (API or web API) that conforms to the constraints of REST architectural style and allows for interaction with RESTful web services. REST stands for representational state transfer and was created by computer scientist Roy Fielding.

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What is the main purpose of JavaScript?

JavaScript is a text-based programming language used both on the client-side and server-side that allows you to make web pages interactive. Where HTML and CSS are languages that give structure and style to web pages, JavaScript gives web pages interactive elements that engage a user.

What is rest parameters in JavaScript?

The rest parameter syntax allows a function to accept an indefinite number of arguments as an array, providing a way to represent variadic functions in JavaScript.

What is a rest operator?

It can be used in two different ways; as a spread operator OR as a rest parameter . Rest parameter: collects all remaining elements into an array. Spread operator: allows iterables( arrays / objects / strings ) to be expanded into single arguments/elements.

How many states a promise can have?

A promise may be in one of 3 possible states: fulfilled, rejected, or pending. Promise users can attach callbacks to handle the fulfilled value or the reason for rejection. Promises are eager, meaning that a promise will start doing whatever task you give it as soon as the promise constructor is invoked.

What is rest operator in TypeScript?

A rest parameter allows you a function to accept zero or more arguments of the specified type. In TypeScript, rest parameters follow these rules: A function has only one rest parameter. The rest parameter appears last in the parameter list. The type of the rest parameter is an array type.

What can I use instead of a spread operator?

TLDR: Object.

One of the alternatives to the spread operator is the Object. assign function. Here is the same function using the object. assign function.

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