allAboutArray.js

/* 
// How to see the output of an array in JavaScript

var vowels = ["a", "e", "i", "o", "u"];
console.log("The output of the array 'vowels' is:", vowels);

// Output || The output of the array 'vowels' is: [ 'a', 'e', 'i', 'o', 'u' ] 
*/



/* 
// We can find the 'Length' of an array in JavaScript; it means, we can see in the output how many elements an array carries

var vowels = ["a", "e", "i", "o", "u"];
console.log("The length of the array 'vowels' is:", vowels.length);

// Output || The length of the array 'vowels' is: 5 
*/



/* 
// Finding an element of an array by its 'Index (Position) Number'
// Note: Index number of any array is begun with Zero (0).

var numbers = [45, 68, 78, 56, 89, 98];
console.log("Element of index number 0 (First Element) of the array 'numbers' is:", numbers[0]);
console.log("Element of index number 1 (Second Element) of the array 'numbers' is:", numbers[1]);
console.log("Element of index number 2 (Third Element) of the array 'numbers' is:", numbers[2]);
console.log("Element of index number 3 (Fourth Element) of the array 'numbers' is:", numbers[3]);

// Output || Element of index number 0 (First Element) of the array 'numbers' is: 45 
// Output || Element of index number 1 (Second Element) of the array 'numbers' is: 68 
// Output || Element of index number 2 (Third Element) of the array 'numbers' is: 78 
// Output || Element of index number 3 (Fourth Element) of the array 'numbers' is: 56 


// This can be shown by storing it into a variable
var fifthItem = numbers[4];
console.log("Element of index number 4 (Fifth Element) of the array 'numbers' is:", fifthItem);

// Output || Element of index number 4 (Fifth Element) of the array 'numbers' is: 89  
*/




/* 
// In JavaScript, If we want to find an element from an array whose element does not exist in that array, what will happen? ==> It will result in 'undefined' in the output

var numbers = [45, 68, 78, 56, 89, 98]; // Index number from '0' to '5'
var getItem = numbers[7];
console.log("Element of index number 7 (Eighth Element) of the array 'numbers' is:", getItem);

// Output || Element of index number 7 (Eighth Element) of the array 'numbers' is: undefined  
*/



/* 
// Setting a new value of an element of an array by using Index Number

var numbers = [45, 68, 78, 56, 89, 98];
console.log("The array 'numbers', before setting a new value:", numbers);

// Output || The array 'numbers', before setting a new value: [ 45, 68, 78, 56, 89, 98 ]

numbers[1] = 77; 
numbers[3] = 44; 
console.log("The array 'numbers', after setting new values in the position number 1 (second element) and position number 3 (fourth element)", numbers);

// Output || The array 'numbers', after setting new values in the position number 1 (second element) and position number 3 (fourth element) [ 45, 77, 78, 44, 89, 98 ] 
*/



/* 
// Suppose, we have two different arrays. We can re-assign the value of the elements of the first array (oldNumbers) by the value of the elements of the second array (newNumbers). We have to use the Index Number in this case.

var oldNumbers = [45, 68, 78, 56, 89, 98];
var newNumbers = [6, 8, 10, 12];

console.log ("The firs array (oldNumbers), before re-assigning values:", oldNumbers);

// Output || The firs array (oldNumbers), before re-assigning values: [ 45, 68, 78, 56, 89, 98 ] 

// Re-assigning the value of some elements of the first array (oldNumbers) by using the value of the elements of the second array (newNumbers)
oldNumbers[2] = newNumbers[1];

// Now the second element of the second array (newNumbers) is the third element of the first array (oldNumbers)
console.log("After re-assigning, the first array (oldNumbers) now:", oldNumbers);

// Output || After re-assigning, the first array (oldNumbers) now: [ 45, 68, 8, 56, 89, 98 ] 
*/



/* 
// Using the Index Number, we can add a new element of an array in any position (not only in the first or in the last).

var numbers = [2, 4, 6, 8];
console.log("The array 'numbers', before adding a new element:", numbers);

// Output || The array 'numbers', before adding a new element: [ 2, 4, 6, 8 ]

numbers[4] = 10; // This is almost as like as setting up a new value to a variable
console.log("The array 'numbers', after adding a new element in the position 4 (Fifth Element):", numbers);

// Output || The array 'numbers', after adding a new element in the position 4 (Fifth Element): [ 2, 4, 6, 8, 10 ]

// Exceptional case :: Empty Index Position
numbers[7] = 20;
console.log("The array 'numbers', after adding a new element in the position 7 (Eighth Element):", numbers);

// Output || The array 'numbers', after adding a new element in the position 7 (Eighth Element): [ 2, 4, 6, 8, 10, <2 empty items>, 20 ]

// Will result in 'undefined'
console.log("Element of Index Number 5 (Sixth Element):", numbers[5]);
// Output || Element of Index Number 5 (Sixth Element): undefined

console.log("Element of Index Number 6 (Seventh Element):", numbers[6]);
// Output || Element of Index Number 6 (Seventh Element): undefined 
*/



// Finding the Index (position) Number of an array in JavaScript by using the 'indexOf()' method

var numbers = [45, 68, 78, 56, 89, 98];
var positionIndex = numbers.indexOf(89);
console.log("Index (position) Number of the element '89' is:", positionIndex);

// Output || Index (position) Number of the element '89' is: 4

// It will result in '-1' if the asking array element does not exist inside of an array
var positionIndexNew = numbers.indexOf(188);
console.log("Index (position) Number of the element '188' is:", positionIndexNew);

// Output || Index (position) Number of the element '188' is: -1