-JavaScript_Recipes/JavaScript Outlines/loops.js at master · john-azzaro/-JavaScript_Recipes · GitHub

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"use strict";

// OBJECTIVE ////////////////////////////////////////////////////////////////////////////////////////////////

// Study Loops, how they work, what use cases do they have, etc.

// SUMMARY //////////////////////////////////////////////////////////////////////////////////////////////////

// What is the problem?:

// Study loops

// What is the BEST solution?

// Find the most efficient way to use a loop.

// What are the special components of these solutions?:

// 1. "for" statment -- meant to iterate while incrementing or decrementing.

// example: [counts up]

// for (let i=0; i <= countTo; i++) {code looped through}

// example: [counts down]

// for (let i = countFrom; i >= 0; i-- ) {code looped through}

// 2. "for... of" -- creates a loop through iterable objects like arrays, maps, etc.

// 3. "for... in" -- meant to enumerate through object properties.

// What needs work?

// 1. Add more loop examples (i.e for...in, etc.) from research.

// 2. Add use case scenarios.

//////////////////////////////////////////////////////////////////////////////////////////////////////////////

///// STANDARD FOR LOOP UP (INCREMENTING) //////////////////////////////////////////////

function countUp() {

const countTo = 10;

for (let i=0; i <= countTo; i++) {

console.log(i);

}

console.log("FOR loop incrementing UP")

console.log(countUp());

///// STANDARD FOR LOOP DOWN (DECREMENTING) //////////////////////////////////////////////

function countDown() {

const countFrom = 10;

for (let i = countFrom; i >= 0; i-- ) {

console.log(i);

}

console.log("FOR loop decrementing DOWN")

console.log(countDown());

///// LOOP USING THE forEach() METHOD ////////////////////////////////////////////////////

function arrayLoop () {

const myArray = ["Tom", "Dick", "Harry"];

return myArray.forEach((element, index) => console.log(`the element ${index} is ${element}`));

}

console.log("FOR Loop iterating through an array");

console.log(arrayLoop());

///// FOR...IN... LOOPING THROUGH AN OBJECT ///////////////////////////////////////////////////////////

const myObject = {

fruit: "apple",

drink: "water",

desert: "cookie",

}

for (let key in myObject) {

console.log(`the key ${key} is ${myObject[key]}`);

}

var object = { "key1" : "one", "key2" : "two", "key3" : "three" },

key = "";

for (key in object) {

console.log(key); // "key1", "key2", "key3"

console.log( object[key] ); // "one", "two", "three"

}

///// LOOPING THROUGH AN OBJECT USING OBJECT.KEYS ////////////////////////////////////////////////////

const mySecondObject = {

hat: "baseball cap",

shirt: "long sleeves",

pants: "jeans",

}

Object.keys(mySecondObject)

// for (let{variable of declaration} character{temporary variable that is redeclared EVERY time through the loop} of string{iterable object we want to iterate through})

// so we'll iterate through every character of string one by one and set each character equal to the temporary variable "character".

// we then take that character and add it on to the start of the string reversed

// then after the entire for loop, we return reversed

function tester(string) {

let reversed = ''; // string that will be assembled over time

for (let character of string) {

reversed = character + reversed;

}

return reversed;

}

console.log(tester('this is a test'));

-JavaScript_Recipes/JavaScript Outlines/loops.js at master · john-azzaro/-JavaScript_Recipes · GitHub

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