Function currying in JavaScript is a functional programming technique that allows you to transform a function that takes multiple arguments into a sequence of functions, each taking a single argument. The curried function returns a new function with some of the arguments already applied. This can be useful in various scenarios and offers several advantages: 1. Readability and Reusability: Curried functions can lead to more readable code, as they allow you to focus on one argument at a time. Additionally, they promote code reusability by creating specialized functions that can be easily reused throughout the codebase. 

function add(a) {
  return function(b) {
    return a + b;
  };
}

const addFive = add(5); // Returns a new function that adds 5 to its argument

console.log(addFive(20)); // Output: 25
console.log(addFive(10)); // Output: 15

or

console.log(add(5)(10)) // output: 15
2. Composability: Currying enhances function composability. You can easily combine multiple curried functions to create more complex functions. This is especially useful in functional programming paradigms. 

function multiply(a) {
  return function(b) {
    return a * b;
  };
}

const multiplyByTwo = multiply(2);
const multiplyByThree = multiply(3);

const result = multiplyByThree(multiplyByTwo(5));
console.log(result); // Output: 30 (3 * 2 * 5)
3. Improved Error Handling: Curried functions can help with error handling by allowing you to validate arguments early on in the process. This can lead to more robust and predictable code. 

function divide(a) {
  return function(b) {
    if (b === 0) {
      throw new Error('Cannot divide by zero!');
    }
    return a / b;
  };
}

const divideByTwo = divide(2);

console.log(divideByTwo(4)); // Output: 2
console.log(divideByTwo(0)); // Throws an error: Cannot divide by zero!
Conclusion: Function currying in JavaScript provides a way to create more flexible, composable, and reusable functions. It's a powerful technique that enhances functional programming and can lead to cleaner and more maintainable code.