What Is Execution Context in Javascript?

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In today’s post, I am going to write about how javascript works. We will throw some light on terminologies like Execution context, function level execution context, function invoking, and threads.

Do you know what happens behind the scene when you run a javascript code?

Let’s take an example of the below code snippet.

https://gist.github.com/c8dc2561b8078487a6fdfd0fd9f0cc95

EC : Execution Context

When we run this code, here is what the Javascript engine does.

  • First, a Global Execution Context is going to be created.
  • Interpreter encounters call x(), and again a new EC is created for x.
  • Now the EC for x is created it will run the code line by line inside x.
  • Inside x, a new function call y() is invoked, it again creates an EC for y.
  • When y is finished running, it will back to EC of x, and variable t is assigned.
  • After x run is finished, it will be back to Global EC, and variable r is assigned.
  • Global EC finishes running and the program stops.

In tomorrow’s blog, I will explain how the call stack works in Javascript. I would love to know your feedback on this blog.

Stay tuned — Follow me on Twitter

Cheers !

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