Imagine you're the owner of a restaurant and you're trying to run the business smoothly. To do so, you have to take care of many things at the same time: greeting customers, taking orders, cooking food, managing the staff, and so on.
Similarly, when you run a JavaScript program, many things are happening at the same time, such as function calls, variable assignments, and error handling. All these tasks need to be organized and managed properly to ensure the program runs smoothly. This is where the concept of execution context comes in.
Execution context is like the environment in which a JavaScript program runs. It includes many things, such as the values of variables, functions, and objects that are available at a certain point in time, as well as the rules for how the code is executed. When a function is called, a new execution context is created for that function. This context contains all the necessary information for that function to run properly.
Let's illustrate this with a story:
You're the owner of a restaurant, and you have a team of chefs who are responsible for cooking the food. Each chef has their own set of tools, such as knives, pans, and ovens. They also have their own recipe books that they follow to cook the food.
One day, a customer comes in and orders a pizza. You assign the task to one of your chefs, who starts cooking the pizza according to their recipe book. While the chef is cooking, they need to access the tools they need to make the pizza, such as the oven and the pizza cutter. They also need to know the ingredients and recipe for the pizza. All this information is available in their own environment, or execution context.
Now, imagine another customer comes in and orders a burger. You assign the task to another chef, who starts cooking the burger according to their own recipe book. This chef has their own set of tools and ingredients that are different from the first chef's, but they can still use them because they are available in their own execution context.
In this story, the chefs are like functions in JavaScript, and their tools and recipe books are like variables, functions, and objects in the execution context. Each chef has their own environment or execution context in which they can access the tools and information they need to complete their tasks.
Similarly, each function in JavaScript has its own execution context in which it can access the variables and functions it needs to complete its tasks. When the function is finished executing, its execution context is removed from the stack, and the program continues to run in the previous context.
In summary, The execution context is like the environment in which a JavaScript program runs, and it includes all the necessary information for the program to run properly, such as variables, functions, and objects. Each function has its own execution context in which it can access the information it needs to complete its tasks.