Shulou(Shulou.com)06/03 Report--

This article will explain in detail how to judge whether it is a browser or a node environment. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Window is undefined in node; setImmediate is defined, not defined in browsers

Timer phase: this phase executes setTimeout and setInterval

Check phase: execute setImmediate

Macro task [task] Macro tasks: script (page code), setTimeout, setInterval, Imax O event, UI interactive event (click event)

Micro task [job] microtasks: Promise, process.nextTick, Promise (). Then ()

Macro tasks can have multiple queues

There is only one queue for microtasks

Between setTimeout tasks, the smaller the number of milliseconds delayed, the higher the queue

In node, timers (setTimeout, setInterval) takes precedence over setImmediate

SetTimeout (() = > {console.log ('setTimeout')}, 0); / / when greater than 1000, setImmediatesetImmediate (() = > {console.log (' setImmediate')}) console.log ('start'); setTimeout (function () {console.log (' timeout');}, 10); new Promise ((resolve) = > {console.log ('promise'); resolve () setTimeout () = > {console.log (setTimeout' in' Promsie);}, 0) }) .then (() = > {console.log ('then');}); console.log (' end')

Operation mechanism

1. Perform a macro task in the execution stack.

two。 When a micro task is encountered during execution, the micro task is added to the micro task queue.

3. When the current macro task is finished, the tasks in the micro-task queue are executed immediately.

4. When the task in the current micro-task queue is finished, check the rendering, and the GUI thread takes over the rendering.

5. After rendering, the js thread takes over, starts the next event loop, and executes the next macro task (fetched from the event queue).

This is the end of the article on "how to judge whether it is a browser or a node environment". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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