higher order function javascript

 a function calling another funciton and function as argument it comes under higher order funcitons

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In JavaScript, higher-order functions are functions that can take other functions as arguments or return functions as their results. They provide a powerful way to abstract and manipulate behavior, allowing for more flexible and reusable code.
Here are some common examples of higher-order functions in JavaScript:
Callback Functions: A higher-order function can accept a function as an argument, often referred to as a callback function. The higher-order function can then invoke the callback function at a certain point or pass data to it. Callback functions are commonly used in asynchronous operations, event handling, and array iteration methods like forEach, map, filter, and reduce.
function higherOrderFunction(callback) {
  // Do some operations
  callback();
}

function callbackFunction() {
  console.log('Callback function is called');
}

higherOrderFunction(callbackFunction);

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2. Function Composition: Higher-order functions can be used to compose multiple functions together to create new functions. This allows for combining and reusing functionality.

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function multiplyByTwo(x) {
  return x * 2;
}

function addThree(x) {
  return x + 3;
}

function compose(f, g) {
  return function(x) {
    return f(g(x));
  };
}

const multiplyByTwoAndAddThree = compose(addThree, multiplyByTwo);
console.log(multiplyByTwoAndAddThree(4)); // Output: 11

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In this example, the compose function takes two functions, f and g, and returns a new function that applies the composition of f and g to its argument. The resulting function, multiplyByTwoAndAddThree, first multiplies the input by 2 and then adds 3 to the result.

3. Currying: Higher-order functions can be used to implement currying, which is a technique where a function with multiple arguments is transformed into a sequence of functions, each taking a single argument. This allows for partial function application and creating specialized versions of the original function.

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

const multiplyByTwo = multiply(2);
console.log(multiplyByTwo(5)); // Output: 10

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In this example, the multiply function takes an argument a and returns a new function that multiplies its argument b by a. By calling multiply(2), we create a specialized version of the multiply function that multiplies its argument by 2. We can then use multiplyByTwo to multiply any number by 2.

Higher-order functions provide a flexible and powerful way to work with functions in JavaScript. They allow for code reuse, composability, and enable advanced functional programming techniques. Understanding and utilizing higher-order functions can lead to more concise and expressive code.