Functional Programming with Javascript
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The document explains functional programming (FP) in JavaScript, focusing on concepts such as pure functions, side effects, and higher-order functions. It contrasts FP with object-oriented programming, highlighting the stateless and function-centric nature of FP. Additionally, the document discusses the advantages and disadvantages of FP, including easier reasoning and testing versus potential limitations in certain situations.
Functional Programming with Javascript
- 1. Functional Programming With JavaScript Deepankar Chopra Senior Software Engineer Ticketmaster
- 2. » What is Functional Programming? » Mutations » Side-Effects » Pure Functions » Higher Order Functions » Composition » Advantages & Disadvantages of FP » How does FP differ from Object-Oriented programming 2Overview
- 3. What is Functional Programming? Functional programming (often abbreviated FP) is the process of building software by » composing pure functions, » avoiding » shared state, » mutable data » side-effects. » Managing state flows through composition 3
- 4. Mutations Mutable is a type of variable that can be changed after it is created. In JavaScript, only objects and arrays are mutable, not primitive values. (You can make a variable name point to a new value, but the previous value is still held in memory.) 4
- 5. Mutations 5 let a = { foo: 'bar' }; let b = a; a.foo = 'test’; console.log(a,b); //{foo: "test"} {foo: "test"} // avoiding mutation let a = { foo: 'bar' }; let b = Object.assign({}, a); a.foo = 'test’; console.log(a,b); //{foo: "test"} {foo: "bar"}
- 6. Side Effects If a program / function modifies the state of something else (outside its own scope), then it is producing a side effect. This could effectively include something like "display a character on the screen", or it could be changing the value stored in some arbitrary RAM location, or anything similar. 6
- 7. Side Effects include » Modifying any external variable or object property (e.g., a global variable, or a variable in the parent function scope chain) » Logging to the console » Writing to the screen » Writing to a file » Writing to the network » Triggering any external process » Calling any other functions with side-effects 7
- 8. Pure Functions » Must return a value » Can’t produce any side-effects » Must return the same output for a given input 8
- 9. Pure Functions Example 9 let a = 10; function impure1(x) { return x + a; } function impure2(x) { a = 30; return x + a; } console.log(impure1(10));//20 a+=10; console.log(impure1(10));//30 console.log(impure2(10));//40 function pure(x, y) { return x + y; } console.log(pure(10,10));
- 10. Composition Function Composition is a mathematical concept, by which the result of one function becomes the input of the next, and so on. Composing functions together is like putting together a series of pipes for our data to flow through. 10
- 11. Composition Example function addOne(x) { return x + 1; } function timesTwo(x) { return x * 2; } console.log(addOne(timesTwo(3))); //7 11
- 12. Higher Order Functions A higher-order function is a function that does at least one of the following: » takes one or more functions as arguments » returns a function as its result. 12
- 13. Higher Order Functions Example function greaterThan(n) { return function(m) { return m > n; }; } let greaterThan10 = greaterThan(10); let greaterThan11 = greaterThan(11); console.log(greaterThan10(11));//true console.log(greaterThan11(11));//false 13
- 14. Advantages of FP » Pure functions are easier to reason about » Testing is easier, and pure functions lend themselves well to techniques like property-based testing » Debugging is easier » Programs are more bulletproof » Programs are written at a higher level, and are therefore easier to comprehend » Parallel/concurrent programming is easier 14
- 15. Disadvantages of FP » Not suitable in every situation » Needs to be clubbed with Object oriented programming in some cases. » Makes heavy use of recursion 15
- 16. How does FP differ from OOP 16 Functional Programming » Primary Manipulation Unit is “Function” » Stateless Programming Model » Functions with No-Side Effects » Order of execution is less importance Object Oriented Programming » Primary Manipulation Unit is Objects(Instances of Classes) » Stateful Programming Model » Methods with Side Effects » Order of execution is more important.
- 17. Any questions? You can mail me at [email protected] 17THANKS!