JavaScript: Create a new string from a given string taking the last 3 characters and added at both the front and back

JavaScript Basic: Exercise-26 with Solution

Write a JavaScript program to create a string from a given string. This is done by taking the last 3 characters and adding them at both the front and back. The string length must be 3 or more.

This JavaScript program creates a new string from a given string by taking its last three characters and appending them both at the front and back. It first checks if the length of the given string is three or more characters to ensure the operation is valid. Then, it extracts the last three characters and concatenates them with the original string, forming the desired result.

Visual Presentation:

Sample Solution:

JavaScript Code:

// Define a function named front_back3 that takes a parameter str
function front_back3(str) {
  // Check if the length of str is greater than or equal to 3
  if (str.length >= 3) {
    // Set str_len to 3
    str_len = 3;
    // Extract the last three characters of str
    back = str.substring(str.length - 3);
    // Return the concatenation of back, str, and back
    return back + str + back;
  } else {
    // If the length of str is less than 3, return false
    return false;
  }
}

// Log the result of calling the front_back3 function with the argument "abc" to the console
console.log(front_back3("abc"));

// Log the result of calling the front_back3 function with the argument "ab" to the console
console.log(front_back3("ab"));

// Log the result of calling the front_back3 function with the argument "abcd" to the console
console.log(front_back3("abcd")); 

Output:

abcabcabc
false
bcdabcdbcd

Live Demo:

See the Pen JavaScript: added characters added at both the front and back-basic- ex-25 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

// Using ES6 arrow function syntax to define the front_back3 function
const front_back3 = (str) => {
  // Check if the length of str is greater than or equal to 3
  if (str.length >= 3) {
    // Set str_len to 3
    const str_len = 3;
    // Extract the last three characters of str
    const back = str.substring(str.length - 3);
    // Return the concatenation of back, str, and back
    return back + str + back;
  } else {
    // If the length of str is less than 3, return false
    return false;
  }
};

// Log the result of calling the front_back3 function with the argument "abc" to the console
console.log(front_back3("abc"));

// Log the result of calling the front_back3 function with the argument "ab" to the console
console.log(front_back3("ab"));

// Log the result of calling the front_back3 function with the argument "abcd" to the console
console.log(front_back3("abcd"));

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