no-magic-numbers should allow passing magic numbers to specific functions like setTimeout

I propose a new option for the no-magic-numbers rule:

{
    "ignoreParamsForFunctions": [
        "setTimeout",
        "setYear"
    ]
}

In this case the following code would be valid:

setTimeout(function () {
    (new Date()).setYear(1984)
}, 500)

In contrary to https://github.com/eslint/eslint/issues/4236 this option would only target specific functions. There are probably not many functions where magic numbers are ok but in my case I just want to omit // eslint-disable-line no-magic-numbers which I currently have to add every single time I use setTimeout.

[aubergine10]

Code that does animations is another example of where it’s often difficult to find meaningful descriptions for numbers, and trying to have a named variable actually makes the code incredibly confusing. In many situations, the number is derived by trial and error to get a value that “feels right” rather than some thoughtful, describable process. In such scenarios, the magic number is actually the most descriptive way to convey what the number is: a magic number. Also, in these scenarios, the main focus of someone reading the code is not what the numbers mean (it’s pretty obvious due to context) but rather being able to clearly see the flow of the animation code and reason about its intent; a load of wordy number constants can actually make such code very difficult to read.

Being able to define some exceptions to the rule like suggested in OP would be beneficial in such scenarios.

[ilyavolodin]

I can sort of understand setYear example that you provided. Even with that I’m having a trouble convincing myself it’s not a magic number, because while it’s clear that 1984 is a year, it’s not clear why you chose 1984 and not 1882. However, why do you think 500 is not a magic number? The reason for setting timeout to 500ms is completely magical to me. Why not 502?

This rule is very strict and hard to follow 100%, but that’s exactly it’s intention. It exists to create self-documenting code. And self-documenting code requires explanation for each number you choose.