How to get numeric value from a prompt box? [duplicate]

parseInt() or parseFloat() are functions in JavaScript which can help you convert the values into integers or floats respectively.

Syntax:

 parseInt(string, radix);
 parseFloat(string); 

• string: the string expression to be parsed as a number.
  
• radix: (optional, but highly encouraged) the base of the numeral system to be used - a number between 2 and 36.

Example:

 var x = prompt("Enter a Value", "0");
 var y = prompt("Enter a Value", "0");
 var num1 = parseInt(x);
 var num2 = parseInt(y);

After this you can perform which ever calculations you want on them.

JavaScript will "convert" numeric string to integer, if you perform calculations on it (as JS is weakly typed). But you can convert it yourself using parseInt or parseFloat.

Just remember to put radix in parseInt!

In case of integer inputs:

var x = parseInt(prompt("Enter a Value", "0"), 10);
var y = parseInt(prompt("Enter a Value", "0"), 10);

In case of float:

var x = parseFloat(prompt("Enter a Value", "0"));
var y = parseFloat(prompt("Enter a Value", "0"));

var xInt = parseInt(x)

This will return either the integer value, or NaN.

Read more about parseInt here.

You have to use parseInt() to convert

For eg.

  var z = parseInt(x) + parseInt(y);

use parseFloat() if you want to handle float value.

You can use parseInt() but, as mentioned, the radix (base) should be specified:

x = parseInt(x, 10);
y = parseInt(y, 10);

10 means a base-10 number.

See this link for an explanation of why the radix is necessary.

Working Demo Reading more Info

parseInt(x) it will cast it into integer

x = parseInt(x);
x = parseInt(x,10); //the radix is 10 (decimal)

parseFloat(x) it will cast it into float

Working Demo Reading more Info

x = parseFloat(x);

you can directly use prompt

var x = parseInt(prompt("Enter a Number", "1"), 10)