JavaScript: Find the first not repeated character

JavaScript Function: Exercise-23 with Solution

Find First Non-Repeated Character

Write a JavaScript function to find the first not repeated character.

Sample arguments : 'abacddbec'
Expected output : 'e'

Visual Presentation:

JavaScript Code:

// Define a function named find_FirstNotRepeatedChar that finds the first non-repeated character in a given string
function find_FirstNotRepeatedChar(str) {
  // Convert the input string into an array of characters
  var arra1 = str.split('');
  
  // Initialize variables result and ctr for storing the result and counting character occurrences
  var result = '';
  var ctr = 0;
 
  // Iterate through each character in the array
  for (var x = 0; x < arra1.length; x++) {
    // Reset the counter (ctr) for each character
    ctr = 0;
 
    // Iterate through the array again to count occurrences of the current character
    for (var y = 0; y < arra1.length; y++) {
      // Check if the current character is equal to the character at position y
      if (arra1[x] === arra1[y]) {
        // If true, increment the counter (ctr)
        ctr += 1;
      }
    }
 
    // Check if the counter (ctr) is less than 2 (character occurs only once)
    if (ctr < 2) {
      // If true, assign the current character to the result and break out of the loop
      result = arra1[x];
      break;
    }
  }
  
  // Return the first non-repeated character found
  return result;
}

// Log the result of calling find_FirstNotRepeatedChar with the input string 'abacddbec' to the console
console.log(find_FirstNotRepeatedChar('abacddbec')); 

Output:

e

Flowchart:

Live Demo:

See the Pen JavaScript - Find the first not repeated character-function-ex- 23 by w3resource (@w3resource) on CodePen.

JavaScript Code:

// Function to find the first non-repeated character in a string
function findFirstNotRepeatedChar(str) {
  // Create a hash map to store character occurrences
  var charMap = {};

  // Loop through each character in the string
  for (var i = 0; i < str.length; i++) {
    // Use the character as a key in the hash map
    var char = str[i];
    // Increment the occurrence count for the current character
    charMap[char] = (charMap[char] || 0) + 1;
  }

  // Loop through each character in the string again
  for (var i = 0; i < str.length; i++) {
    // If the occurrence count for the current character is 1, it is the first non-repeated character
    if (charMap[str[i]] === 1) {
      return str[i];
    }
  }

  // If no non-repeated character is found, return null or a specified value
  return null; // You can modify this line if you want to return a different value
}

// Example usage:
var result = findFirstNotRepeatedChar('abacddbec');
console.log(result); // Output: 'e'

Output:

e

Flowchart:

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds the first non-repeated character in a string by building a frequency map.
• Write a JavaScript function that identifies the first character that does not repeat in a string while ignoring case differences.
• Write a JavaScript function that finds the first non-repeated character using a two-pass algorithm over the string.
• Write a JavaScript function that returns the first non-repeated character in a string and gracefully handles empty string inputs.

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