javascript - Percentage chance of saying something?

Question

I want to write a program that:

• 80% of the time will say sendMessage("hi");
• 5% of the time will say sendMessage("bye");
• and 15% of the time will say sendMessage("Test");

Does it have to do something with Math.random()? like

if (Math.random() * 100 < 80) {
  sendMessage("hi");
}
else if (Math.random() * 100 < 5) {
  sendMessage("bye");
}

Answer 1

Yes, Math.random() is an excellent way to accomplish this. What you want to do is compute a single random number, and then make decisions based on that:

var d = Math.random();
if (d < 0.5)
    // 50% chance of being here
else if (d < 0.7)
    // 20% chance of being here
else
    // 30% chance of being here

That way you don't miss any possibilities.