var, let, none?

Hi, I was wondering if there is any difference in the following lines when in Bangle.js:

var a = 1;
let b = 2;
c = 3;

Additionally, are there any performance differences between == and ===?

var/let are handled the same in Espruino (that's something that will change at some point though). c=3 creates a GLOBAL variable, even if you're in a function.

There shouldn't be a big performance different either way between == and ===.

What about const?

const x = 1;

After assignment x can not be changed. Though I think you can get away with it in an app if you are just uploading an app file to storage. If you try do a pull request the automated build will kick out any assigments of x after the initial assignment.

It's best to look at an actual JS reference:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/var
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/let
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const

But in Espruino, var, let and const are treated the same. Eventually this will change but right now you can assign to a const, although as @HughB says it's a good idea to use as the linter can still check it and throw up errors

Yeah I understand how they work in other Javascript environments, I was curious about espruino specifically.

As long as there aren't any disadvantages to using let and const in espruino I'll continue to use them since that is what I usually use in JavaScript these days.

The only disadvantage is that because right now Espruino doesn't treat let as 'scoped', if you minify the code, occasionally the minifier can make optimisations that break the code :(

Okay, that's good to know. Thanks