Variables are the absolute base of programming. We wouldn't be able to do much without variables. We can find it in all the advanced concept of p...
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constdefines a constant. Constants are not variables. The clue is in the names:In Javascript
constis a bit misleading. It does not define a constant, but it's a one-time assignment. It's a constant reference to a value.Because of this you can not change constant primitive values, but you can change properties of a constant object.
Most people don't understand that when it comes to learning, the most important is not be absolutely true but to make connection between notions.
Can you tell me why almost every article/tuto/course I found by googling "What's a variable" explains constant as "a type of variables"? By doing that we tell the readers that what he just learned with variables is still valid for constants but one thing changes: he can't change the value of a constant. He doesn't have to know more when he just started to learn to code.
Also, what I find interesting in the JS documentation is the sentence:
It seems like, here, a constant is a variable.
Not at all - it is a constant holding (or having a reference to) one 'thing'. The fact that the thing can be changed internally doesn't mean it isn't still the same 'thing' (like if I change my shoes from blue to red, I'm still me). The 'thing' that the constant is 'storing' cannot be changed to a different 'thing'.
This is the fundamental difference between 'variables' and 'constants' and should be taught right from the start so as to avoid any confusion later. It isn't difficult, the names describe the behaviour. A variable is variable, a constant stays constant
When the article say:
It's not clear enough?
The issue is with referring to a constant as a variable. This is simply wrong and generates unnecessary confusion. Your description of the behaviour of a constant however, is completely acceptable
Then, you can start a proposal to change that in the TC39 and Ecma 262 specifications because they are currently referring to a constant as a variable:
source: tc39.es/ecma262/#sec-let-and-const...
A javascript specification (that defines at a technical level the way a
constis implemented in the language) and how best to teach programming concepts to beginners are 2 entirely different things :)Here's something fun to show people. Watch how long the JSON string becomes between an array and an object in these two scenarios:
var a = [];
a[1111] = 1234;
a[2222] = 1234;
console.log(JSON.stringify(a));
as opposed to:
var a = {};
a[1111] = 1234;
a[2222] = 1234;
console.log(JSON.stringify(a));
Key point -- you'll often want to use objects instead of arrays.
I'm going to be nitpicky.
Variables in JavaScript do not have types. They have values, and those values have types. This is important to understand JavaScript, as it is to understand other dynamically typed languages; there is no restriction on which types of values any given variable can take on.
JavaScript does not do any inference, as it has no static type system. This is called reflection, and it is not a guess -- the language is mandated to keep the bookkeeping records which make it possible to determine, dynamically, what the type of any value is (again, not variable, but value).
Thanks for reading and sharing your thoughts. I really appreciate.
Talking about if it's the variable or its value that has a type is like asking if it's the egg or the chicken that appears first. Given that in JavaScript a variable always has a value and a value always has a type, I think we can say a variable has a type even if this type can change (when the value change though).
👌 This is a fantastic introduction to variables in Javascript, Nathanaël! 🙌You've done an excellent job of breaking down the concept in a way that's easy to understand, making it a valuable resource for those new to the language. I'm looking forward to reading more of your insightful posts in the future!
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