Explain the concept of partial application
TL;DR
Partial application is a technique in functional programming where a function is applied to some of its arguments, producing a new function that takes the remaining arguments. This allows you to create more specific functions from general ones. For example, if you have a function add(a, b), you can partially apply it to create a new function add5 that always adds 5 to its argument.
function add(a, b) {return a + b;}const add5 = add.bind(null, 5);console.log(add5(10)); // Outputs 15
Partial application
Partial application is a functional programming technique where a function is applied to some of its arguments, producing a new function that takes the remaining arguments. This can be useful for creating more specific functions from general ones, improving code reusability and readability.
Example
Consider a simple add function that takes two arguments:
function add(a, b) {return a + b;}
Using partial application, you can create a new function add5 that always adds 5 to its argument:
const add5 = add.bind(null, 5);console.log(add5(10)); // Outputs 15
How it works
In the example above, add.bind(null, 5) creates a new function where the first argument (a) is fixed to 5. The null value is used as the this context, which is not relevant in this case.
Benefits
- Code reusability: You can create more specific functions from general ones, making your code more modular and reusable.
- Readability: Partially applied functions can make your code easier to read and understand by reducing the number of arguments you need to pass around.
Real-world example
Partial application is often used in libraries like Lodash. For example, Lodash's _.partial function allows you to create partially applied functions easily:
const _ = require('lodash');function greet(greeting, name) {return `${greeting}, ${name}!`;}const sayHelloTo = _.partial(greet, 'Hello');console.log(sayHelloTo('John')); // Outputs "Hello, John!"