While loop - JavaScript

Question

let age = "";
while (age !== NaN) {
 age = prompt("what is your age");
 Number(age);
}

I can not leave the while loop although I write a number in the prompt box, why?

• Pointy: You initialize age to a string, and the return value from prompt() is also always a string, and no string is ever === to NaN. The call to Number(age) has no effect; you probably want age = Number(age);.

Answer 1

You can use isNaN() function to determine whether a value is NaN or not. You have to add age == "" as part of the condition with || to pass for the initial value (empty string).

The condition should be:

while (isNaN(age) || age == "")

You also have to re-assign the converted value to the variable.

let age = "";
while (isNaN(age) || age === "") {
 age = prompt("what is your age");
 if(age == null)
 break;
 else
 age = Number(age);
}

• H.A.A: let age = ""; while (isNaN(age) || age == "") { age = prompt("what is your age"); age = Number(age); } is a good solution. But whats is wrong with age === "" (with 3 equal signs). I leave the loop when I click Cancel or OK without writing. let age = ""; while (isNaN(age) || age === "") { age = prompt("what is your age"); age = Number(age); }
• Mamun: @H.A.A, when cancel button is clicked age has null value, in that case you have to break the loop.....updated the answer....please check.
• H.A.A: I got it. age = Number(age); changes the type of age to Number that is why age==="" does not work because empty "" is not a number.
• H.A.A: The following code solved my problem: let age = ""; while (isNaN(age) || age == "") { age = prompt("what is your age"); age = Number(age); } let age = ""; while (isNaN(age) || age === "") { age = prompt("what is your age"); if(age == null) break; else age = Number(age); } leaves tho loop without asking the age again.
• Mamun: @H.A.A, does my answer solve your question or you want some thing else?