Why does if condition executes in this requestAnimationFrame code?

[lasjorg]

@shivajikobardan

It says that it doesn’t immediately call the main function but schedule/queue it.

What’s this behavior called in Javascript language? Where can I read more about it. Is this common for every programming language?

requestAnimationFrame takes a callback function. How/when it is called, depends on the API of the higher-order function (i.e. the function/method that takes the callback).

In the case of requestAnimationFrame I believe the “event” that drives it is timing based.

Window: requestAnimationFrame() method - Web APIs | MDN

callback

The function to call when it’s time to update your animation for the next repaint. The callback function is passed one single argument, a DOMHighResTimeStamp similar to the one returned by performance.now(), indicating the point in time when requestAnimationFrame() starts to execute callback functions.

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For a more broad look into scheduling/queuing by the engine/runtime.

What the heck is the event loop anyway? | Philip Roberts | JSConf EU

The event loop - JavaScript | MDN