Why does the Promise object block rendering?

Question

I was testing the Promise object and wrote some code that simulates a long running task that is synchronous. I was comparing Promise and setTimeout - see fiddle:

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Answer 1

while (Date.now() - nu < 1000) {} doesn't simulate a long running task that is syncronous. It is a long running task that is syncronous.

Promises are a way to manage asynchronous code, not a way to make code asynchronous, nor a way to simulate multithreading.

For that, you need to look at workers.

• Web Workers for browsers.
• Worker Threads for Node.js.