How do i make a space between vars in JavaScript?

var r1 ="999999999999999999999999999999999999999999999999999999999999999999999"; // makes var with numbers
var l1 = r1.length; // makes a var. it doesnt calculate it just counts the length of the numbers. this is 69 because there are 69  9's
document.write(l1); // it writes it on your screen/executes the code? im not sure what is this im 12
var r2 ="moop"; // makes a var with letters by using "" i think. i still use it for numbers aswell anyway.
var s1 = r2.substring(1, 4) // it only starts showing from the second letter to the fourth. that will make oop
document.write(s1); // same as the above. only its a different var

document.write( "+(var1)+ " " + (var2)+ " " + (var3)+"); /* another way

const name = "John";
console.log(`Hello, ${name}!`);
// Prints: Hello, John!

console.log(`I am ${2019-1991} years old.`);
// Prints: I am 28 years old.