Difference javascript and typescript

javascript.js

/** example */
function addition(a, b) {
    const result = a + b;
    return console.log(typeof result, result);
}
const num1 = 10;
const num2 = "20";

addition(num1, num2); // log: string 1020

typescript.ts

/** example */
function addition(a: number, b:number) {
    const result = a + b;
    return console.log(typeof result, result);
}
const num1 = 10;
const num2 = "20";

addition(num1, num2); // error