Does the prompt return by default String correct? The function Number does the return conversion of the prompt that is String to number. So when I run the following function and I put numbers in quotes does the message NaN appear, should not I convert the return to number and execute the calculation?
var num = Number(prompt("Digite um número", ""));
alert("Seu número é a raíz quadrada de " + num * num); The problem is that you are not seeing the string that will be interpreted by parseInt .
An input of 12 in prompt will be as if you typed:
let texto = "12";
But an input of "12" is as if it had written:
let texto = "\"12\""; //ou texto = '"12"';
Note that it has quotation marks inside% s of% itself as one of its characters. So when string tries to convert it gets a parseInt and fails because it is not numeric, resulting in " - Not a Number .
Test:
let texto = "12";
let texto2 = "\"12\"";
console.log(parseInt(texto));
console.log(parseInt(texto2));