How do I use rest and spread syntax in JavaScript?

How do I use rest and spread syntax in JavaScript?

Rest and spread syntax are two powerful features in JavaScript that allow you to work with arrays and objects more efficiently. Rest syntax allows you to collect multiple elements into an array, while spread syntax allows you to expand an array or object into individual elements.

Can you give me an example of rest syntax?

Sure! Here's an example of rest syntax:

function sum(...numbers) {
  return numbers.reduce((acc, num) => acc + num, 0);
}
console.log(sum(1, 2, 3, 4)); // Output: 10

In this example, ...numbers collects all arguments into an array.

What about spread syntax?

Here's an example of spread syntax:

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const combined = [...arr1, ...arr2];
console.log(combined); // Output: [1, 2, 3, 4, 5, 6]

In this case, ...arr1 and ...arr2 expand the arrays into individual elements.

Are there any common use cases for these syntaxes?

Yes, common use cases include merging arrays, copying objects, and handling function arguments more flexibly. They help make your code cleaner and more readable.