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
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
Reverse a string using ↴
split() method → splits a string into an array of substrings.
reverse() method → reverses the order of the elements in an array.
join() method → returns an array as a string.
split() method splits a string into an array of substrings based on a specified separator (delimiter). The original string is unchanged.
("") separator → string is split between each character.
(" ") separator → string is split at each space character, resulting in an array of words.
const str3 = "Hello"; → string
str3.split(""); returns ↴
["H", "e", "l", "l", "o"] → array
const str4 = "Hello World"; → string
str4.split(" "); returns ↴
["Hello", "World"] → array
reverse() method reverses the order of the elements in an array.
const arr2 = ["Hello", "World"];
arr2.reverse(); returns ↴
["World, "Hello"] → array
join() method joins all elements of an array into a single string with a specified separator between each element. The original array is unchanged.
("") separator → returns a string joined with no spaces between each character.
(" ") separator → returns string joined with a single space between each element.
const arr3 = ["H", "e", "l", "l", "o"]; array
arr3.join(""); returns ↴
"Hello" → string
const arr4 = ["Hello", "World"]; array
arr4.join(" "); returns ↴
"Hello World" → string
Chaining these 3 built-in functions together ↴
const str5 = "Hello"; → string to be reversed
str5.split("").reverse().join(""); returns ↴
"olleH" → string
Initialize a variable to hold the string to be reversed.
const string1 = "Cry over spilled milk"; → user input
Define a function reverseWords to reverse a string of words.
function reverseWords(str) {}
The function takes a string as input str and returns a new string with the words in reverse order.
Split the string str into an array of words based on spaces.
str.split(" ")
Reverse the array of words.
.reverse()
Join the reversed array back into a string with spaces in between.
.join(" ")
Call the function with ↴
reverseWords(string1);
Reverse order of words.
const string1 = "Cry over spilled milk";
function reverseWords(str) {
return str.split(" ").reverse().join(" ");
}
call function
reverseWords(string1); returns ↴
"milk spilled over Cry"
Alternative to remove spaces from both ends of the string using trim() method and a regular expression as the separator to split the string into an array of words using one or more spaces.
const string2 = " Cry over spilt milk ";
function reverseWords2(str) {
return str.trim().split(/\s+/).reverse().join(" ");
}
call functionreverseWords2(string2); returns ↴
"milk spilled over Cry"