Give Alert after typing the word "pass"

Question

How can I run an Alert after the user writes "stack".

For example, stack (without being an input, just writing) it gives an Alert.

I would have to use keypress and which to check the keys that are being typed, but how can I save each letter until the word beats?

Answer 1

Simply put, this is what you can do:

var memoria = "";
window.onkeyup = function(e) {
    letra = String.fromCharCode(e.keyCode); // Capture a letra digitada
    memoria += letra;                       // Adicione no final da memória
    memoria = memoria.substr(-5);           // Mantenha apenas as 5 ultimas letras
    if (memoria == "STACK") {
        alert("Parabéns!")
    }
}

With each keystroke, get the corresponding letter and store it in a string. When the end of this string matches the password, do something.

Just take care to wipe that memory so it doesn’t grow absurdly. In this example, it is always kept at a maximum of 5 characters, since this is the length of the password.

Answer 2

My solution is similar to Guilherme Bernal’s, but clears the keystroke buffer if you take too long between a letter and another:

var intervaloMaximo = 2000;
var timestamp = Date.now();
var palavra = "";

function tecla(e) {
    var agora = Date.now();
    if(agora - timestamp <= intervaloMaximo) {
         palavra += String.fromCharCode(e.which);
    } else {
         palavra = String.fromCharCode(e.which);
    }

    timestamp = agora;
    
    // Seu alert
    if(palavra === 'STACK') alert('stack!');
    
    // monitorando a palavra digitada
    // para fins demonstrativos
    document.getElementById('palavra').innerHTML = palavra;
}

document.addEventListener('keyup', tecla);

<div id="palavra"></div>