Introduction to Spread and Rest
In JavaScript, spread and rest operators (...) are versatile additions introduced in ES6. They might look the same, but they serve different purposes depending on where and how they're used.
Here is a quick comparison of the two:
| Spread | Rest | |
|---|---|---|
| What it does | "Spreads" elements of an iterable (like an array or string) into places where zero or more elements are expected. | Represents an indefinite number of arguments as an array. |
| Where it's used | In function calls and array literals. | In function parameters and destructuring assignments. |
The Spread Operator
The spread operator 'spreads' elements of an iterable (like an array or string).
Here's an example of how you might use the spread operator:
const array1 = ['A', 'B', 'C'];
const array2 = [...array1, 'D', 'E']; // Spread array1 into array2
console.log(array2); // Output: ['A', 'B', 'C', 'D', 'E']The Rest Operator
The rest operator, on the other hand, is used to represent an indefinite number of elements as an array.
Here's how you can use the rest operator in a function:
function sum(...args) { // args is an array with all arguments passed to the function
return args.reduce((prev, current) => prev + current, 0);
}
console.log(sum(1, 2, 3, 4)); // Output: 10Conclusion
While they may look similar, the spread and rest operators in JavaScript serve different, but equally useful purposes. The spread operator helps us manipulate and expand elements in an iterable, while the rest operator allows us to represent an indefinite number of arguments as an array. Both operators offer cleaner, more concise syntax for tasks that were more complex in earlier versions of JavaScript.
