HTML
<input id="num">Please enter number
<button id="sub">
submit
</button>
Javascript
let num = document.querySelector("#num");
//user input
let sub = document.querySelector("#sub");
//on click
sub.addEventListener("click", ()=>
{
//output user input
console.log(num.value);
})
https://jsfiddle.net/gkarxnoq/How to convert input strings into numbers only.
let num = document.querySelector("#num");
//user input
let sub = document.querySelector("#sub");
//on click
sub.addEventListener("click", ()=>
{
let n = +num.value;
//output user input
//if you enter a non number will produce different errors;
//if you enter space will produce 0
//if you enter a letter will produce a NAN
console.log(n);
})
https://jsfiddle.net/gkarxnoq/1/If the user enters a non number, then will be using the !num and return statement to return invalid.
Note: Nothing happens when a user enters Strings or any non digit number.
let num = document.querySelector("#num");
//user input
let sub = document.querySelector("#sub");
//on click
sub.addEventListener("click", ()=>
{
let n = +num.value;
//output user input
if(!n)
{
return;
}
console.log(n);
})
https://jsfiddle.net/gkarxnoq/2/