Function Parameters in JavaScript

Function parameters in JavaScript are used to pass values into functions. These values can be utilized within the function to perform operations or return results. Understanding function parameters is essential for creating flexible and reusable code.

Basic Function Parameters

Function parameters are defined in the function declaration and used to accept values passed to the function:

function greet(name) {
  return `Hello, ${name}!`;
}

console.log(greet('Alice')); // Output: Hello, Alice!

The function greet takes a single parameter name.
The function returns a greeting message using the provided name.
Parameters can be used within the function to perform operations based on the values passed.

Default Parameters

JavaScript allows you to define default values for function parameters. If no value is provided for a parameter, the default value is used:

function multiply(a, b = 1) {
  return a * b;
}

console.log(multiply(5));   // Output: 5 (b defaults to 1)
console.log(multiply(5, 2)); // Output: 10

The function multiply has a default value for the parameter b.
If b is not provided, it defaults to 1.

Rest Parameters

Rest parameters allow you to handle an indefinite number of arguments as an array. They are defined using the ... syntax:

function sum(...numbers) {
  return numbers.reduce((acc, num) => acc + num, 0);
}

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

The function sum uses the rest parameter ...numbers to accept any number of arguments.
These arguments are then processed as an array within the function.

Parameter Destructuring

Parameter destructuring allows you to extract values from objects or arrays passed as arguments into a function:

function displayUser({ name, age }) {
  console.log(`Name: ${name}, Age: ${age}`);
}

displayUser({ name: 'John', age: 30 }); // Output: Name: John, Age: 30

The function displayUser uses parameter destructuring to extract name and age from the object passed as an argument.
This approach simplifies extracting and using multiple properties from an object.

Conclusion

Understanding function parameters, including default values, rest parameters, and destructuring, enhances your ability to write versatile and efficient JavaScript functions. Mastering these concepts will allow you to handle various input scenarios and make your functions more robust and adaptable.

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