How can I test if a letter in a string is uppercase or lowercase using JavaScript?

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How can I test if a letter in a string is uppercase or lowercase using JavaScript?

The answer by josh and maleki will return true on both upper and lower case if the character or the whole string is numeric. making the result a false result. example using josh

var character = '5';
if (character == character.toUpperCase()) {
 alert ('upper case true');
}
if (character == character.toLowerCase()){
 alert ('lower case true');
}

another way is to test it first if it is numeric, else test it if upper or lower case example

var strings = 'this iS a TeSt 523 Now!';
var i=0;
var character='';
while (i <= strings.length){
    character = strings.charAt(i);
    if (!isNaN(character * 1)){
        alert('character is numeric');
    }else{
        if (character == character.toUpperCase()) {
            alert ('upper case true');
        }
        if (character == character.toLowerCase()){
            alert ('lower case true');
        }
    }
    i++;
}

How can I check if a string is all uppercase in JavaScript?, To test if a letter in a string is uppercase or lowercase using javascript, you can simply convert the char to its respective case and see the result. How can I test if a letter in a string is uppercase or lowercase using JavaScript? Answers: The answer by josh and maleki will return true on both upper and lower case if the character or the whole string is numeric. making the result a false result.

if (character == character.toLowerCase())
{
  // The character is lowercase
}
else
{
  // The character is uppercase
}

How to test if a letter in a string is uppercase or lowercase using , JavaScript String: Exercise-43 with Solution. Write a JavaScript function to test whether the character at the provided Next: Write a JavaScript function to test whether the character at the provided character index is lower case. What is const tips_remove = (arr, func) => { for (const [i, val] of arr.entries()) if  Here is a method to convert string to Uppercase using ASCII in JavaScript. As seen in the above code, you converted the passed in string to an array. You check for each letter if its in lower case ASCII code range 97-122. If its in lowercase, you convert it to uppercase ASCII by deducting 32.

This will log true if character is uppercase letter, and log false in every other case:

var letters = ['a', 'b', 'c', 'A', 'B', 'C', '(', ')', '+', '-', '~', '*'];

​​​for (var ​i = 0; i<letters.length; i++) {
    if (letters[i] === letters[i].toUpperCase()
        && letters[i] !== letters[i].toLowerCase()) {
        console.log(letters[i] + ": " + true);
    } else {
        console.log(letters[i] + ": " + false);
    }
}​

You may test it here: http://jsfiddle.net/Axfxz/ (use Firebug or sth).

​​​for (var ​i = 0; i<letters.length; i++) {
    if (letters[i] !== letters[i].toUpperCase()
        && letters[i] === letters[i].toLowerCase()) {
        console.log(letters[i] + ": " + true);
    } else {
        console.log(letters[i] + ": " + false);
    }
}​

and this is for lowercase:).

JavaScript: Test whether the character at the provided character , JavaScript exercises, practice and solution: Write a JavaScript program to test the first character of a string is uppercase or not. Something which is close to your original idea. You basically just check whether there is a part in the string which contains an upper case letter - there can be any other characters after and before it. Here I included a small main method for testing purposes.

The problem with the other answers is, that some characters like numbers or punctuation also return true when checked for lowercase/uppercase.

I found this to work very well for it:

function isLowerCase(str)
{
    return str == str.toLowerCase() && str != str.toUpperCase();
}

This will work for punctuation, numbers and letters:

assert(isLowerCase("a"))
assert(!isLowerCase("Ü"))
assert(!isLowerCase("4"))
assert(!isLowerCase("_"))

To check one letter just call it using isLowerCase(str[charIndex])

JavaScript validation with regular expression: Check whether the , How can I check if a character is lower case or upper case or alpha - numeric? help. I want to translate my Python codes about string checking. characters if you compare a character to both its lowercase and uppercase versions: Also, I had started learning JS from Codecademy about a month ago when they were  String's first character is uppercase String's first character is not uppercase Flowchart: Live Demo: See the Pen javascript-regexp-exercise-1 by w3resource (@w3resource) on CodePen. Improve this sample solution and post your code through Disqus. Previous: JavaScript Regular Expression exercises

const isUpperCase = (string) => /^[A-Z]*$/.test(string)

then :

isUpperCase('A') // true
isUpperCase('a') // false

How can I check if a character is lower case or upper case or alpha , and Usage. The toUpperCase() method converts a string to uppercase letters. Tip: Use the toLowerCase() method to convert a string to lowercase letters. Definition and Usage. The toLowerCase() method converts a string to lowercase letters. Note: The toLowerCase() method does not change the original string. Tip: Use the toUpperCase() method to convert a string to uppercase letters.

JavaScript String toUpperCase() Method, Note: The toLocaleUpperCase() method does not change the original string. Tip: Use the toLocaleLowerCase() method to convert a string to lowercase letters,  Capitalize the First Letter of a String in JavaScript using ES6+(ECMAScript) features: Capitalize the first letter of a string in JavaScript by Overriding String Prototype: Best way to make the first letter of a string to uppercase in JavaScript: Capitalize the First Letter of a String using simple Javascript: To capitalize the first letter of

JavaScript String toLocaleUpperCase() Method, The toUpperCase() method returns the calling string value converted to uppercase (the value will be converted to a string if it isn't one). is generated from structured data. If you'd like to contribute to the data, please check out toLocaleLowerCase() · String.prototype. Last modified: Mar 26, 2020 , by MDN contributors. So try creating a class for that, so you can use it globally, for example: .first-letter-uppercase and add something like below in your CSS:.first-letter-uppercase:first-letter { text-transform:capitalize; } Also the alternative option is JavaScript, so the best gonna be something like this:

String.prototype.toUpperCase(), This function is used to check if the argument contains any uppercase letters string character by character upto its length, check if character is in lowercase or​  In this article, you'll learn how to uppercase or lowercase a string completely in JavaScript. JavaScript provides two built-in functions for converting strings to uppercase and lowercase. Let us look at them. toUpperCase() Method. The toUpperCase() method transforms a string to uppercase letters in JavaScript. It doesn't change the original string and returns a new string equivalent to the string converted to uppercase.

Comments
  • can i just clarify the question - you want to test if a particular letter in a string is upper or lower - or do you want to test if the whole string contains any letter that is uppercase or lowercase. if it is the latter then how do you propose getting the result without looping through the string and testing one letter at a time?
  • jsperf.com/isupper-comparison/5 A few ideas there, and you can test them for speed as well.
  • Idea #4 ([:upper:]) is fast and very cool except that it doesn't work, see my comment below and my corrected jsperf.com/isupper-comparison/7.
  • str == str.toUpperCase(); returns true or false
  • Won't you still have the same false result if the character is something neither numeric nor alpha, such as punctuation?
  • @LarsH see this: stackoverflow.com/questions/1027224/…
  • This is a really old question but what's up with the random 'ch' var?
  • This code will alert that punctuation characters like ! are numeric.
  • @JS That's a typo, meant to be var character='';
  • strings.ToUpper(character) != character throws error invalid operation mismatched string and uint8 in golang 1.9.
  • The most rigorous test given here so far. +1
  • BTW, also works with accented characters like "É", "Ñ", and "ñ".
  • Unfortunately, there are lowercase letters that don't have an uppercase variant (and probably the other way around as well). The German 'ß' is a lowercase letter, but if you apply the second function on it, it will result in a false.
  • Don't know why the other answers are voted. This is the only solution I could think of as well - the logic being "does the character have upper && lower case variants? If so then return whether it's upper or lower case"