how to add numbers when calling a function in html code example

Example 1: html make phone number callable

Area code with dashes, 1 and + sign

<a href="tel:+1-555-555-1212">555-555-1212</a>
Area code with no dashes, 1 and + sign

<a href="tel:+15555551212">555-555-1212</a>

Example 2: to add 2 numbers using function in javascript

// Prints the sum of 2 float numbers 
function addition(number_1, number_2)
{
  int sum = number_1 + number_2
document.write(sum)
}

var number_1 = parseFloat(prompt("First Number"));
var number_2 = parseFloat(prompt("Second Number"));
addition(number_1, number_2);