Execution contexts
Now it's time to look at the JavaScript interpreter itself—the component that takes over from other browser components when events take place and code needs to run. There's always an active JavaScript context, and within the interpreter, we'll find a stack of contexts. This is similar to many programming languages where stacks control the active context.
Think of the active context as a snapshot of what's happening right now in our JavaScript code. A stack structure is used because the active context can change to something else, such as when a function is called. When this happens, a new snapshot is pushed onto the stack, becoming the active context. When it's done running, it's popped from the stack, leaving the next context as the active context.
In this section, we'll take a look at how the JavaScript interpreter handles context switching, and the internal job queue that manages the context stack.
Maintaining execution state
The...
