Create a random number between 1-6

 const randomNumber = Math.floor(Math.random() * 6) + 1 // 0-5 -> 1-6
 function getRandomInt(x){
    return Math.floor(Math.random() * x);
}
getRandomInt(10)

Covert a string to an array

let str = "Apple";
const arr = str.split("")

Covert an array to a string

Concatenation of all elements of the array:

["e", "l", "p", "p", "a"].join("")

Swap Operation

let temp = array[i];
array[i] = array[i+1];
array[i+1] = temp;

Removing Spaces from a character

function cleanUpSpaces(str) {
    return str.replace(/\s/g, '')
}

Use 'for of' Loop to iterate through a string or an array

• Use for of Loop to iterate through a string or an array

let string = "Ambreen" for(let char of string){ console.log(char) }

Use 'for in' Loop to iterate through an object

const charMap = {
    'car': 'Toyota Corolla',
    'model': '2022'
}
for(let key in charMap){
    console.log('Key: ', key, 'Value: ', charMap[key])
}

Working with key/values in JS object

const keys = Object.keys(courses);
// print all keys
console.log(keys);
// [ 'java', 'javascript', 'nodejs', 'php' ]
// iterate over object
keys.forEach((key, index) => {
    console.log(`${key}: ${courses[key]}`);
});

Using indexOf method to determine index position

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
console.log(beasts.indexOf('bison')); //1

Sort a number Array

    // https://www.w3schools.com/js/js_array_sort.asp
    // By default, the sort() function sorts values as strings.
    // You can fix this by providing a compare function
    array.sort((a,b) => a-b);

Build Character Map

function buildCharMap(str) {
  const charMap = {};
  for (let char of str) {
    charMap[char] = charMap[char] + 1 || 1;
  }
  return charMap;
}

Compare the size of 2 character maps

if (Object.keys(aCharMap).length !== Object.keys(bCharMap).length) {
    return false;
}

Getting values for all keys from a hash map

Object.values(anagramMap)

Converting Set to array

function intersection(nums1, nums2) {
const set = new Set(nums1);
  const filteredSet = new Set(nums2.filter((n) => set.has(n)));
    return [ ...filteredSet ];
}

Filtering out the alphabet character only

// Filtering out the alphabet character only:
function filterAlphbetOnly(str){
    const regex = /[a-zA-Z]/g;
    let filteredArr = str.match(regex);
    let reversedArr = reverseArr(filteredArr);
    return reversedArr;
}

JS Filter Method

const age = [23, 45, 20, 20, 55, 65];
// console.log(age.filter(age40AndAbove));
console.log(age.filter((age)=> {
    return age >= 40
}));

Merge two or more arrays

The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array

const array1 = ['a', 'b', 'c'];
const array2 = ['d', 'e', 'f'];
const array3 = array1.concat(array2);
console.log(array3);
// expected output: Array ["a", "b", "c", "d", "e", "f"]

Common Mathematics functions

Math.abs() The Math.abs() function returns the absolute value of a number. That is, it returns x if x is positive or zero, and the negation of x if x is negative.

Math.sign()  The Math.sign() function returns either a positive or negative +/- 1, indicating the sign of a number passed into the argument. If the number passed into Math.sign() is 0, it will return a +/- 0. Note that if the number is positive, an explicit (+) will not be returned. (returns 1 if number is positive else returns -1)

Math.max() The Math.max() function returns the largest of the zero or more numbers given as input parameters

The Math.floor() function returns the largest integer less than or equal to a given number.

Using filter Function

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];
const filterList = (arr) => {
    const filteredIntegers = arr.filter(num => Number.isInteger(num) && num > 0);
    return filteredIntegers;
};
const filteredIntegers = filterList(realNumberArray);
console.log(filteredIntegers);

Using map & filter functions together

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];
const squareList = (arr) => {
  const squaredIntegers = arr.filter(num => Number.isInteger(num) && num > 0).map(x => x * x);
  return squaredIntegers;
};
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);

Setting default value

const increment = (function() {
  return function increment(number, value = 1) {
    return number + value;
  };
})();
console.log(increment(5, 2)); 
console.log(increment(5));

Using Rest Operator for Function Parameter

const sum = (function() {
  return function sum(...args) {
    return args.reduce((a, b) => a + b, 0);
  };
})();
console.log(sum(1, 2, 3, 4));

Using the Spread Operator to make a copy of an array

• Spreads out an array (i.e. makes a copy) into its individual parts

//Original array is mutated
const arr1 = ['JAN', 'FEB', 'MAR', 'APR', 'MAY'];
let arr2;
(function() {
  arr2 = arr1; 
  arr1[0] = 'potato'
})();
console.log(arr2); //outputs: ["potato", "FEB", "MAR", "APR", "MAY"] as both arr1 & arr2 are still pointing to the same array.
//Here arr2 will NOT be equal to arr1 instead it will be equal to the content of the arr1
const arr1 = ['JAN', 'FEB', 'MAR', 'APR', 'MAY'];
let arr2;
(function() {
  arr2 = [...arr1]; 
  arr1[0] = 'potato'
})();
console.log(arr2);

Destructuring

var voxel = {x: 3.6, y: 7.4, z: 6.54 };
var x = voxel.x; // x = 3.6
var y = voxel.y; // y = 7.4
var z = voxel.z; // z = 6.54
const { x : a, y : b, z : c } = voxel; // a = 3.6, b = 7.4, c = 6.54
const AVG_TEMPERATURES = {
  today: 77.5,
  tomorrow: 79
};
function getTempOfTmrw(avgTemperatures) {
  
  const { tomorrow : tempOfTomorrow } = avgTemperatures; // change this line
  return tempOfTomorrow;
}
console.log(getTempOfTmrw(AVG_TEMPERATURES)); // should be 79

Destructuring from Nested Objects

const LOCAL_FORECAST = {
  today: { min: 72, max: 83 },
  tomorrow: { min: 73.3, max: 84.6 }
};
function getMaxOfTmrw(forecast) {
  "use strict";
  const { tomorrow : { max : maxOfTomorrow }} = forecast; 
  return maxOfTomorrow;
}
console.log(getMaxOfTmrw(LOCAL_FORECAST));

Use Destructuring Assignment to assign variables from Arrays

const [z, x, , y] = [1, 2, 3, 4, 5, 6];
console.log(z, x, y);
//Output: 1,2,4
//Uisng destructuring to switch values
let a = 8, b = 6;
(() => {
  "use strict";
  [a, b] = [b, a]
})();
console.log(a);  //6
console.log(b);  //8

Using Destructuring Assignment with the Rest operator to Reassign Array Element

const source = [1,2,3,4,5,6,7,8,9,10];
function removeFirstTwo(list) {
  const [ , , ...arr] = list; 
  return arr;
}
const arr = removeFirstTwo(source);
console.log(arr); 
console.log(source);
//We can also assign the first two to some variables as below
const source = [1,2,3,4,5,6,7,8,9,10];
function removeFirstTwo(list) {
  const [ a, b, ...arr] = list; 
  return arr;
}
const arr = removeFirstTwo(source);
console.log(arr); 
console.log(source);

Use Destructuring Assignment to Pass an object as a Function's Parameters

const stats = {
  max: 56.78,
  standard_deviation: 4.34,
  median: 34.54,
  mode: 23.87,
  min: -0.75,
  average: 35.85
};
const half = (function() {
  return function half({ max, min }) {
    return (max + min) / 2.0;
  };
})();
console.log(stats); 
console.log(half(stats)); 

Template Literals

function makeList(arr) {
  const resultDisplayArray = [];
    arr.forEach(element => resultDisplayArray.push(`<li class="text-warning">${element}</li>`))
   
    console.log(resultDisplayArray)
  return resultDisplayArray;
}
/**
 * makeList(result.failure) should return:
 * [ `<li class="text-warning">no-var</li>`,
 *   `<li class="text-warning">var-on-top</li>`, 
 *   `<li class="text-warning">linebreak</li>` ]
 **/
const resultDisplayArray = makeList(result.failure);

Write concise Object Literal Declaration uisng simple fileds

//LOng approach
const createPerson = (name, age, gender) => {
  return {
    name: name,
    age: age,
    gender: gender
  };
};
console.log(createPerson("Zodiac Hasbro", 56, "male"));
//Using concise approach:
const createPerson = (name, age, gender) => ({ name, age, gender });
console.log(createPerson("Zodiac Hasbro", 56, "male"));

Write Concise Declarative function

//Concise Way
const bicycle = {
  gear: 2,
  setGear(newGear) {
    "use strict";
    this.gear = newGear;
  }
};
bicycle.setGear(3);
console.log(bicycle.gear);
//Long form:
const bicycle = {
  gear: 2,
  setGear: function(newGear) {
    "use strict";
    this.gear = newGear;
  }
};
bicycle.setGear(3);
console.log(bicycle.gear);

Use class Syntax to define a constructor function

//Using old way
var SpaceShuttle = function(targetPlanet){
  this.targetPlanet = targetPlanet;
}
var zeus = new SpaceShuttle('Jupiter');
console.log(zeus.targetPlanet)
//New approach
class SpaceShuttle {
  constructor(targetPlanet){
    this.targetPlanet = targetPlanet;
  }
}
var zeus = new SpaceShuttle('Jupiter');
console.log(zeus.targetPlanet)
//Another Example
function makeClass() {
  class Vegetable {
    constructor(name){
      this.name = name;
    }
  }
  return Vegetable;
}
const Vegetable = makeClass();
const carrot = new Vegetable('carrot');
console.log(carrot.name);

Using getter & setters to control an access to an object

class Book {
  constructor(author) {
    this._author = author;
  }
  // getter
  get writer(){
    return this._author;
  }
  // setter
  set writer(updatedAuthor){
    this._author = updatedAuthor;
  }
}
//Another Example
function makeClass() {
  class Thermostat {
    constructor(temp) {
      this._temp = 5/9 * (temp - 32);
    }
    get temperature(){
      return this._temp;
    }
    set temperature(updatedTemp){
      this._temp = updatedTemp;
    }
  }
  return Thermostat;
}
const Thermostat = makeClass();
const thermos = new Thermostat(76); 
let temp = thermos.temperature; 
thermos.temperature = 26;
temp = thermos.temperature;

Use export to reuse a code block

const capitalizeString = (string) => {
  return string.charAt(0).toUpperCase() + string.slice(1);
}
export { capitalizeString };
export const foo = "bar";
export const bar = "foo";

Use * to import everything from a file

import * as capitalizeStrings from "capitalize_strings"

Create an Export fallback with export default

export default function subtract(x,y) {return x - y;}

Importing a Default Export

import subtract from "math_functions";

Resources

• https://scrimba.com/learn/es6/