To define rest parameters, we simply prefix the parameter name with three dots (...). This tells JavaScript that any extra arguments passed to the function should be collected into an array.

Here’s an example of a function that uses rest parameters to calculate the sum of multiple numbers:

function sum(...numbers) {
  let result = 0;

  for (let i = 0; i < numbers.length; i++) {
    result += numbers[i];
  }

  return result;
}

console.log(sum(1, 2, 3, 4, 5)); // Output: 15
console.log(sum(10, 20)); // Output: 30

In the above code, the sum function accepts any number of arguments and collects them into the numbers array using rest parameters. We can then loop through the array and calculate the sum of all the numbers.

Rest parameters can also be used with other named parameters in a function. However, it’s important to note that rest parameters must be the last parameter in the function’s parameter list.

function printInfo(name, age, ...hobbies) {
  console.log(`Name: ${name}`);
  console.log(`Age: ${age}`);
  console.log(`Hobbies: ${hobbies.join(", ")}`);
}

printInfo("John", 25, "Reading", "Gardening", "Cycling");

In the above example, the printInfo function accepts name and age as regular parameters, and the rest parameter hobbies will collect any remaining arguments into an array. We can then use the join method to concatenate the hobbies array into a string, separated by commas.

Rest parameters in JavaScript functions provide a flexible and concise way to handle variable numbers of arguments, making our code more adaptable and readable. So, the next time you encounter a situation where you need to handle multiple arguments in a function, consider using rest parameters to simplify your code.

#JavaScript #Functions