JavaScript: Create a new string adding "Py" in front of a given string

JavaScript Basic: Exercise-21 with Solution

Add 'Py' to Start of String if Not Present

Write a JavaScript program to create another string by adding "Py" in front of a given string. If the given string begins with "Py" return the original string.

This JavaScript program creates a new string by adding "Py" in front of a given string. However, if the given string already begins with "Py", it returns the original string without any modification. It checks the initial characters of the given string to determine whether "Py" needs to be added or not.

Visual Presentation:

Sample Solution:

JavaScript Code:

 // Define a function named string_check that takes a parameter str1
function string_check(str1) {
  // Check if str1 is null, undefined, or starts with the substring 'Py'
  if (str1 === null || str1 === undefined || str1.substring(0, 2) === 'Py') {
    // If true, return str1
    return str1;
  }
  // If false, prepend 'Py' to str1 and return the result
  return "Py" + str1;
}

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

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

Output:

Python
Python

Live Demo:

See the Pen JavaScript: Create new string: basic-ex-21 by w3resource (@w3resource) on CodePen.

Flowchart:

ES6 Version:

 // Using ES6 arrow function syntax to define the string_check function
const string_check = (str1) => (str1 === null || str1 === undefined || str1.substring(0, 2) === 'Py' ? str1 : `Py${str1}`);

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

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

Improve this sample solution and post your code through Disqus.

Previous: JavaScript program to check from two given integers, if one is positive and one is negative.
Next: JavaScript program to remove a character at the specified position of a given string and return the new string.