Comparison operators
Comparison operators are used to compare two values, returning either true or false.
== loose equality operator → checks whether its two operands are equal after attempting to perform type coercion.
=== strict equality operator → checks for equality without type conversion, both the value and the type must be exactly the same.
In JavaScript, primitive types (like numbers and strings) are compared by value, while objects (including arrays) are compared by reference.
Arrays are a type of object. When an array is created , a reference to that array is created in memory.
Arrays are compared by reference, not by value.
[1, 2, 3] === [1, 2, 3] → returns false
Arrays are used to store multiple values in a single variable.
Each value is called an element, and each element has a numeric position in the array, known as its index.
Arrays are zero-indexed, meaning the first element is at index 0, the second at index 1, and so on.
Arrays can contain any data type, including numbers, strings, and objects.
const arr1 = [2, 4, 6]; array
arr1[0]; element at index 0 → 2
arr1[1]; element at index 1 → 4
arr1[2]; element at index 2 → 6
arr1[3]; element at index 3 → undefined index not found
Strings are a sequence of zero or more characters written inside quotes used to represent text.
Strings may consist of letters, numbers, symbols, words, or sentences.
Strings are immutable, they cannot be changed.
Each character in a string has an index.
The first character will be index 0 the second character will be index 1 and so on.
There are two ways to access an individual character in a string.
charAt() method
const str1 = "abc"; string
str1.charAt(0); character at index 0 → "a"
str1.charAt(1); character at index 1 → "b"
str1.charAt(2); character at index 2 → "c"
str1.charAt(3); character at index 3 → "" index not found
Alternatively use at() or slice() methods
bracket notation []
const str2 = "abc"; string
str2[0]; character at index 0 → "a"
str2[1]; character at index 1 → "b"
str2[2]; character at index 2 → "c"
str2[3]; character at index 3 → undefined index not found
Numbers are used to represent both integer and floating-point values.
Numbers are most commonly expressed in literal forms like 255 or 3.14159 ↴
let num1 = 5; → number
let num2 = 2.5; → number
let num3 = num1 + num2;
console.log(num3); returns ↴
7.5 → number
Compare two arrays for equality using ↴
for loop → executes a block of code a number of times.
length property → sets or returns the number of elements in an array.
for loop repeatedly executes a block of code until a specified condition evaluates to false.
The loop runs a block of code a set number of times, defined by an initialization, a condition, and an increment.
for (let x = 0; x < 4; x++) {
console.log(x);
}
Loop variable x is initialized to 0
Condition x < 4 is checked before each iteration.
The loop will continue to run as long as x is less than 4
The loop repeatedly executes a block of code 4 times, from 0 to 3
For each iteration of the loop, the current value of x is printed to the console.
After each iteration, x is incremented by 1 x++
When x reaches 4 the condition evaluates to false, terminating the loop.
0
1
2
3 → printed to console
length property returns the number of elements in an array.
const arr2 = [1, 2, 3, 4, 5, 6];
arr2.length; returns ↴
6 → there are 6 elements in the array
Initialize variables to hold the two arrays to compare for equality.
const array1 = ["Hello", "World", 2, 3]; → user input
const array2 = ["Hello", "World", 2, 3]; → user input
Define a function arraysEqual to compare two arrays for equality.
function arraysEqual(arr) {}
The function takes two arrays as input arr1, arr2 and returns true if both arrays are equal, otherwise returns false. The original arrays are unchanged.
Check if the lengths of the arrays are different.
if (arr1.length !== arr2.length)
If lengths differ, arrays are not equal, return false and end execution of function.
return false
Loop through each element in the first array arr1
for (let x = 0; x < arr1.length; x++) {}
Compare corresponding elements of both arrays.
if (arr1[x] !== arr2[x])
If any element differs, arrays are not equal, return false and end execution of function.
return false
If all checks pass, the arrays are equal, return true
return true
If the function returns true, the arrays are equal ✔
If the function returns false, the arrays are not equal ✖
Call the function with ↴
arraysEqual(array1, array2);
Compare two arrays for equality.
const array1 = ["Hello", "World", 2, 3];
const array2 = ["Hello", "World", 2, 3];
function arraysEqual(arr1, arr2) {
if (arr1.length !== arr2.length) return false;
for (let x = 0; x < arr1.length; x++) {
if (arr1[x] !== arr2[x]) return false;
}
return true;
}
call function
arraysEqual(array1, array2); returns ↴
true