JavaScript: Check whether a string is lower case or not

JavaScript fundamental (ES6 Syntax): Exercise-197 with Solution

Check String Lowercase

Write a JavaScript program to check whether a string is lower case or not.

• Convert the given string to lower case, using String.prototype.toLowerCase() and compare it to the original.

Sample Solution:

JavaScript Code:

// Define a function 'isLowerCase' that checks if the given string 'str' contains only lowercase letters
const isLowerCase = str =>
  // Check if the given string 'str' is equal to its lowercase version
  str === str.toLowerCase();

// Test cases to check if the strings contain only lowercase letters
console.log(isLowerCase('abc'));   // true (all letters are lowercase)
console.log(isLowerCase('a3@$'));  // true (all letters are lowercase)
console.log(isLowerCase('Ab4'));   // false (one letter is uppercase)

Output:

true
true
false

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-197-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that returns true if all alphabetic characters in a string are in lowercase.
• Write a JavaScript function that compares a string to its lowercase version to determine if it is entirely lowercase.
• Write a JavaScript program that filters out non-letter characters and then checks if the remaining string is lowercase.
• Write a JavaScript function that returns a boolean after converting the string and comparing with the original.

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