如何在JS中添加两个变量？

var num1 = 10;
var num2 = 20;
var sum = num1 + num2;
console.log(sum); // 输出30

var str1 = "Hello";
var str2 = "World";
var result = str1 + str2;
console.log(result); // 输出"HelloWorld"

var num = 10;
var str = "20";
var result = num + str;
console.log(result); // 输出"1020"