On the image of variables and classes

The question of whether variables are boxes and their destructive and non-destructive behavior

When you first learned about variables and classes, what was the image you were taught?

When I first learned about them, I was taught that variables are like boxes.

However, this was a little difficult for me to visualize.

The first time I learned this, I was taught that a variable is like a box, but this was a little hard to visualize, because once you put data into a variable, when you took it out, it was separated into copying and extracting data.

For example, let’s say you have this code

// const means constant, a variable declaration that cannot be reassigned
const i = "Hello";
const j = i;

console.log(j); // >>Hello

The data in variable i is copied and passed to j.

At this point, if it were really a box, it would be gone when it is taken out, but in the actual code, it is not.

The j = i is a copy of the data and the data is copied to a memory address in another location and stored.

Copying and extracting are generally called non-destructive or destructive, depending on the method you call.

In this case, since it is an assignment, it is a copy.

In the destructive case, it looks like this

const numbers = [1, 2, 3];
numbers.pop();

Extract the end of the array, i.e., 3.

The variable numbers will be left with [1, 2].

The variable numbers is still [1, 2], so why don’t we imagine the variable as “a chunk of data with a name attached to it”?

Hmmm… if you remember whether it’s destructive or non-destructive, and if you think of a variable as a “box”, you’ll be fine.

I think it would be easier to understand static typing if we use the term “box”, so we should use “box”.

What is the image of a ## class?

When you learn programming to a certain extent, you will encounter a problem.

This is the class.

When you learn several languages, you will commonly hear that a class is “like a blueprint.

To be honest, it is hard to understand. How about “a group of functions and variables that are used as a group”?

If you are aware that a class is like a blueprint, it will be difficult to understand when you learn static methods, so if you remember that a class is used after instantiation, you will be able to get by.

Eventually

The best way to understand is to move your hands, look at the sample code, and then try to create your own variables and classes.