How to use a Map In Javascript

Using a Map, iterate through the string, storing each character as a key and its count as the value. If a character is already in the map, return true; otherwise, continue. If no characters repeat, return false.

Example: In this example we counts duplicate characters in a string using a Map, then prints them or a message if none exist.

JavaScript

const inputStr = "w3wiki";
const charCount = new Map();

// Count occurrences of each character
for (const char of inputStr) {
    if (charCount.has(char)) {
        charCount.set(char, charCount.get(char) + 1);
    } else {
        charCount.set(char, 1);
    }
}

const duplicates = [];

// Find characters with count > 1
for (const [char, count] of charCount) {
    if (count > 1) {
        duplicates.push(char);
    }
}

// Print duplicates or no duplicates message
if (duplicates.length > 0) {
    console.log(`The duplicate characters: ${duplicates.join(', ')}`);
} else {
    console.log(`The string "${inputStr}" has no duplicate characters.`);
}

Output

The duplicate characters: G, e, k, s

JavaScript Program to Check for Repeated Characters in a String

In this article, we are going to see various methods with which you can detect repeated characters in a string. Checking for repeated characters in a string involves examining the string’s content to identify if any character occurs more than once. This helps detect duplications or repetitions within the text.

Input: Str = “w3wiki”
Output:
e, count = 4
g, count = 2
k, count = 2
s, count = 2
Explanation: e,g,k,and s are characters which are occured in string in more than one times.

There are several methods that can be used to Check for repeated characters in a string JavaScript.

Table of Content

Using sort() method with for…of loop
Using a Set in JavaScript
Without using Extra Data Structure
Using a Map
Using Object as a Frequency Counter:

We will explore all the above methods along with their basic implementation with the help of examples.

How to use a Map In Javascript

JavaScript Program to Check for Repeated Characters in a String

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