How to get the number of occurrences of each letter in specified string in JavaScript ?
In this article, we are given a string, our task is to find the occurrence of a character in the string with the help of a user-defined function.
Example:
Input : "hello"
Output : h occur 1 times
e occur 1 times
l occur 2 times
o occur 1 times
Explanation : here "hello" have 1 h, so it have 1 value.
as same e have 1, l have 2 , o have 1.
Example 2:
Input : "did"
Output: d occur 2 times
i occur 1 times
Approach 1: In this approach, we use a map data structure to store the number of times characters occur.
- First, we initialize the map with a key for each character of the string, and the value for each is 0.
- We iterate over the string and increment the value of the character.
- Finally, print key-values of the map.
Example: This example shows the use of the above-explained approach.
<script>
//function to print occurrence of character
function printans( ans )
{
for( let [ key ,value] of ans)
{
// if()
console.log(`${key} occurs ${value} times` );
}
}
// function count occurrence of character
function count( str , outp_map )
{
for( let i = 0 ;i < str.length ;i++)
{
let k = outp_map.get(str[i]);
outp_map.set(str[i], k+1) ;
}
//calling print function
printans(outp_map);
}
//function create map to count character
function count_occurs( test , callback )
{
//checking string is valid or not
if( test.length === 0 )
{
console.log(" empty string ");
return ;
}
else
{
// map for storing count values
let ans = new Map();
for( let i = 0 ;i < test.length;i++)
{
ans.set(test[i], 0);
}
callback( test ,ans);
}
}
// test string
let test = "helloworld";
count_occurs( test ,count);
</script>
Output:
h occurs 1 times
e occurs 1 times
l occurs 3 times
o occurs 2 times
w occurs 1 times
r occurs 1 times
d occurs 1 times
Approach 2: In this approach, we use nested for loop to iterate over the string and count for each character in the string.
- First, initialize count with value 0 for the ith value of the string.
- Now we iterate over the string if ith value matches with the character, increasing the count value by 1.
- Finally, print the value of the count.
Example: This example shows the use of the above-explained approach.
<script>
// function that count character occurrences in string
function count_occur( str )
{
// checking string is valid or not
if( str.length == 0 )
{
console.log("Invalid string")
return;
}
//cor loop to iterate over string
for( let i = 0 ;i < str.length ;i++)
{
//variable counting occurrence
let count = 0;
for( let j = 0 ;j < str.length ;j++)
{
if( str[i] == str[j] && i > j )
{
break;
}
if( str[i] == str[j] )
{
count++;
}
}
if( count > 0)
console.log(`${str[i]} occurs ${count} times`);
}
}
// test string
let test_str = "gfghello";
count_occur( test_str);
</script>
Output:
g occurs 2 times
f occurs 1 times
h occurs 1 times
e occurs 1 times
l occurs 2 times
o occurs 1 times
Approach 3: Using Array.reduce() with Map:
Using Array.reduce() with Map, the approach iterates over each character of the string. It accumulates the count of each character in a Map object, using the character as the key and the count as the value, updating it as needed.
Example: In this example The function countLetters() splits the string into characters, then uses Array.reduce() with a `Map` to count occurrences. Output is a `Map` with letter counts.
function countLetters(str) {
return str.split('').reduce((count, char) => {
count.set(char, (count.get(char) || 0) + 1);
return count;
}, new Map());
}
const result = countLetters("w3wiki");
console.log(result);
Output
Map(7) {
'G' => 2,
'e' => 4,
'k' => 2,
's' => 2,
'f' => 1,
'o' => 1,
'r' => 1
}
Approach 4: Using a Plain JavaScript Object
In this approach, we will use a plain JavaScript object to store the count of each character in the string. This method is similar to using a Map but utilizes a simpler data structure.
Steps:
- Initialize an empty object.
- Iterate over each character in the string.
- If the character is already a key in the object, increment its value.
- If the character is not a key in the object, add it with an initial value of 1.
- Print the key-value pairs from the object.
Example Implementation:
// Function to count occurrences of characters using a plain object
function countOccurrencesWithObject(str) {
// Initialize an empty object to store character counts
let charCount = {};
// Iterate over each character in the string
for (let char of str) {
// If the character already exists in the object, increment its count
if (charCount[char]) {
charCount[char]++;
} else {
// If the character doesn't exist in the object, add it with count 1
charCount[char] = 1;
}
}
// Print the character counts
for (let char in charCount) {
console.log(`${char} occurs ${charCount[char]} times`);
}
}
// Test string
let testString = "hellojavascript";
countOccurrencesWithObject(testString);
Output
h occurs 1 times e occurs 1 times l occurs 2 times o occurs 1 times j occurs 1 times a occurs 2 times v occurs 1 times s occurs 1 times c occurs 1 times r occurs 1 times i occurs 1 times p occurs 1 ti...