An essential point to remember a training course is to take notes and discuss the subject with others. That's why every day I will post on dev.to the concepts and notes that I learned the day before.
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Without further ado here is a summary of my notes for day 4.
Functions
A function is a piece of code that we can be re-use over and over again in our code.
function displayHello() { console.log('Hello World') } // Function can be invoke (run) displayHello() // 'Hello World' // Data can be pass to function function display(greeting) { console.log(greeting) } // Invoke with the data pass as parameter display('Hello World') // 'Hello World' // Function can return value function sumNumber(number1, number2) { return number1 + number2 } console.log(sumNumber(10, 5)) // 15 Function declaration vs function expression
// Function declaration (can be call before declaration) function displayGreeting(greeting) { return 'Hello ' + greeting } // Function expression (can be use in code in place of expression) const displayGreeting = function (greeting) { return 'Hello ' + greeting } Arrow Function
// Shorthand function expression // 1. Remove the function() keyword // 2. Remove curly brace {} // 3. Remove return keyword // 4. Add => between parameters and function body const displayGreeting = greeting => 'Hello ' + greeting // With mutli parameters const addNumber = (number1, number2) => number1 + number2 // With no parameters const displayGreeting = () => 'Hello World' // Multi-lines Arrow function // Bring back the curly brace and return keyword const displayGreeting = (greeting) => { console.log('Hello World') console.log('Hello Mike') return true } Conclusion
That's it for this part. In the next one we will cover Array and Object!
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