Window prompt blocks code execution before it

Question

I've got this code in javascript right before a window.prompt() function. However, the code preceding the prompt is obstructed by the prompt, even though it's before the prompt() function. For example, here's what I'm expecting to see:

console.log('Hello World!');
const prompt = window.prompt(message, defaultText);

Hello World!

*PROMPT OPENS*

However, it does this:

console.log('Hello World!');
const prompt = window.prompt('See how the console.log doesn\'t appear while this is open?', 'Yes, I do see that! Clicking Cancel or Ok then logs it!');

What causes this to happen? I'd understand if the console.log came after the prompt rather than before it.

Any assistance would be greatly appreciated. Thank you.