Javascript in and of itself isn't an asynchronous language because it's single threaded. Read further as I detail how event loop plays a crucial part in Javascript's async behavior.
The event loop is a mechanism that continuously checks the message queue for pending events and executes them in a specific order. It is fundamental to JavaScript's ability to handle asynchronous tasks without freezing the entire program.
Let's consider all the moving pieces:
Thread of execution: JavaScript is single-threaded, meaning it has only one main thread of execution. This thread handles the execution of the program's code.
Call Stack: The call stack keeps track of the currently executing functions. When a function is called, it is added to the top of the stack and is then treated as the first priority function that needs to be resolved by the thread. When a function completes, it is removed from the stack.
Message Queue: The message queue holds a queue of messages that each correspond to a callback function.
Event Loop: The event loop is a continuous orchestrator that checks the call stack and the message queue. The event loop waits till the call stack is empty (no more functions to execute). Whenever that happens, the event loop then looks at the message queue. If there are any messages, the event loop pushes the callback function to the call stack, and then the task of executing that function is in the core domain of JavaScript.
This cycle repeats continuously, allowing JavaScript to handle asynchronous tasks without blocking the main thread. The event loop ensures that the program remains responsive to user interactions and other events, providing a smooth and efficient execution environment.
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