JavaScript: Check a string is in Flat case

JavaScript String: Exercise-53 with Solution

Check Flat Case

Flat case: As the name implies, flatcase refers to the use of lowercase letters, with no spaces between words.
Write a JavaScript function to check a given string is in Flat case or not.
Test Data:
('j') -> true
('java exercises') -> false
('JavaScriptExercises') -> false
('javascriptexercises') -> true
(12356) -> "It must be a string."

Sample Solution:

JavaScript Code:

/**
 * Define a function named test which takes a single parameter 'text'.
 * @param {string} text - The input text to be tested.
 * @returns {boolean|string} - Returns true if the input text contains only lowercase letters, otherwise returns a string message.
 */
const test = (text) => {
  // Check if the input parameter is a string.
  if (typeof text !== 'string') {
    return 'It must be a string.';
  }
  
  // Define a regular expression pattern to match strings containing only lowercase letters.
  const pattern = /^[a-z]*$/;
  
  // Test if the input text matches the defined pattern.
  return pattern.test(text);
};

// Test the function with various inputs and log the results.
console.log(test('j')); // true
console.log(test('java exercises')); // false
console.log(test('JavaScriptExercises')); // false
console.log(test('javascriptexercises')); // true
console.log(test(12356)); // 'It must be a string.'

Output:

true
false
false
true
It must be a string.

Explanation:

In the exercise above,

• The function "test()" takes one parameter, 'text', representing the input text to be tested.
• It begins with a check to ensure that the input parameter is a string. If it's not a string, the function returns the message "It must be a string."
• The function then defines a regular expression pattern (/^[a-z]*$/) that matches strings containing only lowercase letters.
• It applies this pattern using the "test()" method on the input text and returns the result.
• Test cases are provided at the end to illustrate the function's behavior with different inputs.

Flowchart:

Live Demo:

See the Pen javascript-string-exercise-53 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that tests if a string is entirely lowercase with no spaces (flatcase) using regular expressions.
• Write a JavaScript function that validates the input is a string and then compares it to its lowercase version.
• Write a JavaScript function that returns true for strings that match the flatcase pattern and false otherwise.
• Write a JavaScript function that handles numeric inputs by returning an error if the input is not a string.

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