rustdoc: replace var with const and let in JS

[jsha]

Now that rustdoc is using ES6 idioms, we should replace all var declarations with const and let. This style guideline explains why: https://github.com/airbnb/javascript#references. Once that's done, we should turn on the lint checks that enforce it.

I think there are a few places (at least in search.js) where we rely on the surprising property of var declarations called "var hoisting". In those cases we may to move some declarations to the top of their function at the same time we change them to let.

[GuillaumeGomez]

I'll do it once I'm done with #90630.

[the8472]

Shouldn't the JS also be changed to strict mode to ensure that all variables actually are declared via keywords?

[GuillaumeGomez]

@Folyd: So a few things remain to be done:

• Move callback to the () => {} syntax.
• Use "strict" as suggested by @the8472
• Add a lot more eslint lints.

Do you want to divide the work with me? :)

EDIT: sorry @fmease for the invalid ping ^^'

[Folyd]

@Folyd: So a few things remain to be done:

• Move callback to the () => {} syntax.
• Use "strict" as suggested by @the8472
• Add a lot more eslint lints.

Do you want to divide the work with me? :)

EDIT: sorry @fmease for the invalid ping ^^'

Sure, I'd love to. 😸

[GuillaumeGomez]

Then pick one thing and go ahead. :)

[Folyd]

Ok, I pick this one.

Move callback to the () => {} syntax.

[GuillaumeGomez]

Then I'll do "use strict" next.

[GuillaumeGomez]

@Folyd Now remains adding more eslint lints. Let's go one at a time. What do you think? If you're interested, just write down which one you're adding here so that we don't conflict. ;)

[Folyd]

@Folyd Now remains adding more eslint lints. Let's go one at a time. What do you think? If you're interested, just write down which one you're adding here so that we don't conflict. ;)

I just file a new PR to change the way we declare the lint rules. #96805
This can eliminate repeatedly rules declaration if we need to add further lint rules.

[GuillaumeGomez]

This issue is done so closing it.