Javascript: The result is displayed even without data entered by the user!

Question

Well, the idea was the following: make a simple function that computes the value inserted in an input and return the result to the user, but if the value entered is zero, the message that returns is: "Blank value!" ; (Because the " when converted to number becomes zero). In short, is there a way that it works there or I’ll have to rewrite in another way.

function inp() {

    var num = Number(input.value);
    var myNum = (num == " ");

    if (Number.isNaN(num) == true) {
        alert("Formato Inválido!");
    } else if (myNum === true) {
        alert("Valor em branco!")
    } else {
        alert((50 + 50 + 50) * num);
    }
}

Answer 1

You can use a ternary to define num:

function inp() {

    var input = document.querySelector("#ip");
    var num = input.value == '0' ? '0' : Number(input.value);
    var myNum = (num == " ");

    if (Number.isNaN(num) == true) {
        alert("Formato Inválido!");
    } else if (myNum === true) {
        alert("Valor em branco!")
    } else {
        alert((50 + 50 + 50) * num);
    }
}

<input type="text" id="ip" />
<input type="button" value="ok" onclick="inp()" />