prompt has to be a number in javascript

To prompt for a number in javascript, you can use the prompt function to get user input, and then use parseInt to convert the input to an integer. Here's an example:

index.tsx
let numStr = prompt("Enter a number:");
let num = parseInt(numStr);

if (isNaN(num)) {
  alert("Invalid input: please enter a number.");
} else {
  alert("You entered the number " + num);
}
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In this code, we first prompt the user to enter a number using the prompt function. We then use the parseInt function to try to convert the user's input to an integer. If the input is not a number (i.e. NaN), we display an error message using the alert function. Otherwise, we display a success message with the user's input.