add variable to strign javacsript code example

Example 1: how to concatenate strings and variables in javascript

const helloName = name => `Hello ${name}!`

Example 2: concantene number in js

Use "" + 5 + 6 to force it to strings. 
This works with numerical variables too:

var a = 5;
var b = 6;
console.log("" + a + b);