document.querySelector() not working

JavaScript
1

I’m wanting to log the input of a number field. But I keep getting an error that value is null. Why?:
HTML:
<input type="number" id="your-guess" />
JS:
let inputNum = Number(document.querySelector("#your-guess").value); console.log(inputNum)

3

console.log(document.querySelector("#your-guess")); let inputNum = Number(document.querySelector("#your-guess").value);
Typing this code above into the console gives me the error message
Identifier 'inputNum' has already been declared