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
Capitalize first character of each word using ↴
for loop → executes a block of code a number of times.
charAt() method → returns the character at a specified index in a string.
split() method → splits a string into an array of substrings.
slice() method → returns selected elements in an array, as a new array.
join() method → returns an array as a string.
toLowerCase() method → returns the value of the string converted to lower case.
toUpperCase() method → returns the value of the string converted to upper case.
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
toLowerCase() method returns a new string with all letters converted to lower case. The original string is unchanged.
const str3 = "hELlo wORLd";
str3.toLowerCase(); returns ↴
"hello world" → lower case
toUpperCase() method returns a new string with all letters converted to upper case. The original string is unchanged.
const str4 = "hELlo wORLd";
str4.toUpperCase(); returns ↴
"HELLO WORLD" → upper case
toUpperCase() method can be used to capitalize a single letter.
const str5 = "h"; lower case
str5.toUpperCase(); returns ↴
"H" → upper case
charAt() method returns the character at the given index.
If the index is out of range an empty string "" is returned.
const str6 = "hello";
str6.charAt(0); → "h" first character
str6.charAt(1); → "e"
str6.charAt(2); → "l"
str6.charAt(3); → "l"
str6.charAt(4); → "o"
str6.charAt(5); → "" not found
slice() method extracts a part of a string and returns it as a new string, without modifying the original string.
syntax ↴
slice(start) return a new string from start index to end of string
slice(start, end) return a string from start index to end index of string (exclusive).
Return a new string from index 1 to end of string.
const str7 = "hello world";
str7.slice(1); start index is 1
returns ↴
"ello world" → string with first character extracted
Return a new string from index 1 to index 9 (exclusive).
const str8 = "Hello World";
str8.slice(1, 9); start index is 1 end index is 9 (not included)
returns ↴
"ello Wor"
The capitalized first character can then be concatenated with the rest of the string.
"H" + "ello world"
const str9 = "hello world";
str9.charAt(0).toUpperCase() + str9.slice(1); returns ↴
"Hello world" → only the first character of the string is capitalized and not each word.
To capitalize each word in a string we can divide the string into an array of words.
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 str10 = "Hello"; → string
str10.split(""); returns ↴
["H", "e", "l", "l", "o"] → array
const str11 = "hello world"; → string
str11.split(" "); returns ↴
["hello", "world"] → array
Convert the string to lower case before splitting into an array of words.
const str12 = "hELlo wORLd"; string
const word = str12.toLowerCase().split(" ");
console.log(word); returns ↴
["hello", "world"] → 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 arr2 = ["H", "e", "l", "l", "o"]; array
arr2.join(""); returns ↴
"Hello" → string
const arr3 = ["Hello", "World"]; array
arr3.join(" "); returns ↴
"Hello World" → string
Initialize a variable to hold the string to capitalize first letter of each word.
const string1 = "hELlo wORLd"; → user input
Define a function capWords to capitalize first letter of each word.
function capWords(str) {}
The function takes a string as input str and returns a new string with capitalized words. The original string remains unchanged.
Convert str to lower case and split into an array of words.
const word = str.toLowerCase().split(" ") word
Loop through each word element in the array.
for (let x = 0; x < word.length; x++) {}
During each iteration of the loop, each word[x] is re-assigned ↴
The first letter is capitalized and concatenated with the rest of the word.
word[x] = word[x].charAt(0).toUpperCase() + word[x].slice(1)
word[x] → current element being processed in the array
charAt(0).toUpperCase() convert first letter to upper case.
slice(1) append the remaining lower cased letters.
Join the array back into a single string with spaces in between.
return word.join(" ")
Call the function with ↴
capWords(string1);
Capitalize first letter of each word.
const str = "hELlo wORLd"; "hELlo wORLd"
const word = str.toLowerCase() "hello world"
.split(" "); ["hello", "world"]
Iterate through each word element in the array.
for (let x = 0; x < word.length; x++) {}
First iteration of array ↴
word[0] "hello"
charAt(0) "h"
.toUpperCase() "H" +
.slice(1) "ello"
"H" + "ello" → "Hello"
Second iteration of array ↴
word[1] "world"
charAt(0) "w"
.toUpperCase() "W" +
.slice(1) "orld"
"W" + "orld" → "World"
Return array as a string ↴
return word.join(" "); "Hello World"
Capitalize first letter of each word.
const string1 = "hELlo wORLd";
function capWords(str) {
const word = str.toLowerCase().split(" ");
for (let x = 0; x < word.length; x++) {
word[x] = word[x].charAt(0).toUpperCase() + word[x].slice(1);
}
return word.join(" ");
}
call function
capWords(string1); returns ↴
"Hello World"
Alternatives to access an individual character in a string ↴
const myStr = "ABCDE";
myStr.at(2); → "C"
myStr.charAt(2); → "C"
myStr.slice(2, 3); → "C"
myStr.substring(2, 3); → "C"
Alternatives ↴
substring(1) can be used instead of slice(1)
substring(0, 1) can be used instead of charAt(0)