Question

In a web application, how do I determine whether the first letter in a given string is upper- or lower-case using JavaScript?

Answer 1

You can use toUpperCase:

if(yourString.charAt(0) === yourString.charAt(0).toUpperCase()) {
    //Uppercase!
}

If you’re going to be using this on a regular basis, I would suggest putting it in a function on the String prototype, something like this:

String.prototype.isFirstCapital = function() {
    return this.charAt(0) === this.charAt(0).toUpperCase();   
}
if(yourString.isFirstCapital()) {
    //Uppercase!
}

Update (based on comments)

I don’t know what you actually want to do in the case that the string does not being with a letter, but a simple solution would be to add a quick check to see if it does or not, and return false if not:

String.prototype.isFirstCapital = function() {
    return /^[a-z]/i.test(this) && this.charAt(0) === this.charAt(0).toUpperCase();   
}