JavaScript Rest Operator: What Is the Rest Parameter?

A JavaScript **rest parameter** consists of the rest operator (`...`),  and a regular parameter name. The rest parameter can only be present as the last argument to a function.

A visual representation is shown below.

#    
## Rest parameter example

```javascript
// Define a function with two regular parameters and one rest parameter:

function myFruits(fruit1, fruit2, ...otherFruits) { 
  return otherFruits;
}
```
The **rest operator (`...`)** instructs the computer to put the rest of some specific user-supplied arguments into an array. Thus, the remaining arguments can be accessed as part of the array, `otherFruits`. 

As such, we call `...otherFruits` a rest parameter.

## Code

// Define a function with two regular parameters and one rest parameter:
function myFruits(fruit1, fruit2, ...otherFruits) { 
  return otherFruits;
}

// Invoke myFruits function while passing five arguments to its parameters:
const result = myFruits("mango", "strawberry", "apricot", "kiwi", "orange");

console.log(result);


#  Explanation
In the snippet above, `myFruits` was invoked by passing five arguments to the function.

In other words, `"mango"` and `strawberry"` got assigned to `fruit1` and `fruit2` respectively.

At the same time, the rest operator put the remaining arguments (`"apricot"`, `"kiwi"`, and `"orange"`) into an array and assigned that array to the `otherFruits` parameter.

##   
## Rest variable in JS

A JavaScript **rest variable** consists of the rest operator and a regular variable. This is the same as with the rest parameter, except that this is applicable to lists used in a program generally and not just limited to parameters.

// Define a destructuring array with two regular variables and one rest variable:
const [name1, name2, ...otherNames] = [
  "Nina", "Sarah", "Steve", "Mike", "Flora"
];

// Print the rest variable items:
console.log(otherNames); 


## Explanation
In this case, the rest operator (`...`) instructs the program to assign the remaining user-supplied values into an array titled `otherNames`. Thus, `otherNames` is a rest variable.

This can also be applied to array destructuring.

// Define a destructuring object with two regular variables and one rest variable:
const { name1, name2, ...otherNames } = {
  name1: "Nina",
  name2: "Sarah", 
  name3: "Steve",
  name4: "Mike",
  name5: "Flora"
}

// Invoke the otherNames variable:
console.log(otherNames);

// The invocation above will return:
// {name3: "Steve", name4: "Mike", name5: "Flora"}

What are rest parameters and rest variables in JavaScript?

Rest parameters and variables in JavaScript use the rest operator ( ... ) to capture remaining arguments or values into an array.