Hey there! Let's clear this up first: You can't achieve this string manipulation logic with just HTML—you absolutely need JavaScript for this. HTML is a markup language for structuring content, it doesn't have built-in capabilities to process strings, extract characters, or modify text case like you need here.

Why your earlier attempts failed #

You mentioned trying charAt(0), substr (you had a typo with "substrate") or LEFT directly in HTML tags—those are all JavaScript methods (or Excel-style functions that don't work in HTML/JS). They won't work if you try to use them outside of a JavaScript context.

Fixing your code to meet the requirement #

Your existing JS code is a great start—we just need to add the string processing steps to get the first initials and lowercase the university name, then combine them as you want. Here's the updated version:

var firstname = prompt("Enter your first name: ", "");
var lastname = prompt("Enter your last name: ", "");
var univname = prompt("Enter your university name: ", "");

// Extract first initials (uppercase) and lowercase university name
var firstInitial = firstname.charAt(0).toUpperCase();
var lastInitial = lastname.charAt(0).toUpperCase();
var lowerUniv = univname.toLowerCase();

// Build the desired username string
var username = firstInitial + lastInitial + lowerUniv;

if (confirm("Your username is " + username)) {
  document.write("<h1>Thank you for signing up, " + firstname + "!</h1>");
} else {
  document.write("<h1>Have a great day!</h1>");
}

Quick breakdown of the changes: #

• charAt(0) grabs the first character of each name, then toUpperCase() ensures it's capitalized (matching your example's uppercase initials style).
• toLowerCase() converts the university name to all lowercase, just like your example's "mercer".
• We combine these parts into the username variable, which we then use in the confirm prompt.

A quick extra tip: You might want to add checks for empty inputs (in case a user clicks cancel or enters nothing) to avoid unexpected errors, but the above code directly addresses your core requirement.

内容的提问来源于stack exchange，提问作者joey