Microtasks: Why Promises Run First

This is the third article in a series on how JavaScript actually runs. You can read the full series here or on my website . In the last article , we established that: JavaScript execution cannot be interrupted. Once a macrotask starts, nothing cuts in. Only after it completes does the runtime select the next macrotask from the queue. But consider this: setTimeout (() => console . log ( " timeout " ), 0 ); Promise . resolve (). then (() => console . log ( " promise " )); console . log ( " sync do