Coding Diary: JavaScript Learning Log 3

Coding diary to reflect concepts that I am learning and revisiting

Classical Inheritance vs Prototypical inheritance

Prototypical inheritance allows you to create a new object and combine methods from other objects
With classical inheritance you are forced to inherit all the methods pertaining to the parent class whereas prototypical inheritance allows you to choose the methods you would like to inherit

Syntax for Private instance variables

Private variables are variables that cannot be accessed outside of the class that they are in
In JavaScript, private variables start with #

class User {
	#votingAge = 18; // here #votingAge is a private instance variable
}

JavaScript

Private variables also have to be defined outside of the constructor but can be used inside the constructor

E.g.

class User {
	#votingAge;
	
	constructor() {
		this.#votingAge = 18;
	}
}

JavaScript

Private instance methods

These are methods that can only be used inside the class

class User {
	constructor(age) {
		this.age = age;
		this.#logAge();
	}
	#logAge() {
		console.log(this.age);
	}
}

JavaScript

Recap

The some callback method

Returns true if at least one of the elements in the array statisfies the condition
Example: Creating a function that returns true if one of the ages in the array is below 18

const agesInTheGroup = ages = {
	return ages.some(age => age < 18);
}

JavaScript

Recap of map()

Example of using the map.(callback) method.

Given an array of different words return an array length each word in the array

/**
 * @param {string[]} strings
 */
 
const wordsToLengthConverter = words => {
  return words.map(word => word.length):
}
console.log(wordsToLengthConverter(["Hello", "World", "Bonjour"])); // [5, 5, 7]

JavaScript