Is a reversed switch statement acceptable JavaScript?

问题

JSLint is complaining that (true) is a weird condition. Which is understandable if I wasn't using it on a reversed switch statement. So is JSLint wrong or should I not be using reversed switch statements?

Thanks for any help/enlightenment.

switch (true) {
    case (menuLinksLength < 4):
        numberOfColumns = 1;
        break;
    case (menuLinksLength > 3 && menuLinksLength < 7):
        numberOfColumns = 2;
        break;
    case (menuLinksLength > 6 && menuLinksLength < 10):
        numberOfColumns = 3;
        break;
    case (menuLinksLength > 9):
        numberOfColumns = 4;
        break;
    default:
        numberOfColumns = 0;
}

回答1:

The third edition of the ECMA-262 standard (supported by Firefox 1.0+, Google Chrome 1.0+, MSIE 5.5+ and others) defines that

switch (expression) {
    case label1:
        statements1
    .
    .
    .
}

executes statements1 if (expression) matches label1.

That means that your switch statement is perfectly fine.

I tried it out on Firefox, Chrome and IE. None complains...

Edit:

Now the guessing part:

JSLint is a code anaylisis tool. When it sees switch (true), it assumes that you don't know what you're doing. Weird doesn't mean necessarily wrong...

回答2:

Personally I wouldn't like seeing reversed switch in a code base. It doesn't buy you anything when compared to a plain if/elseif block, and its exotic nature can be cause for confusion.

That's also what JSLint is complaining about:

You are doing something unorthodox. Is there a good reason for it? If not, it might be better to stick to the basics.

回答3:

numberOfColumns = Math.max(4, Math.floor(menuLinksLength / 3));

This will give you identical results to your existing code. Your question is fairly ambiguous, as "acceptable" is a very subjective term. I would personally reject any merge request with a reversed switch statement, because I actually can't think of a situation where that couldn't be replaced with something simpler and/or easier to read.

来源：https://stackoverflow.com/questions/7658601/is-a-reversed-switch-statement-acceptable-javascript

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javascript

switch-statement

jslint