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switch(true) gotcha (community.nodebb.org)

submitted 4 weeks ago* (last edited 4 weeks ago) by julian@community.nodebb.org to c/general-discussion@community.nodebb.org

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I discovered this week a little footgun if you happen to use this bit of syntactic sugar:

const object = {
    foo: 'bar',
}

switch (true) {
    case object &amp;&amp; object.foo: {
        // This will never execute
    }

    default:
        // ...
}

The cases in your switch(true) must actually return true, not truthy, for the case to execute.

Using switch(true) is a bit of a controversial coding practice, since it's only meant to replace long if..else if..else chains. Literally has no additional utility except aesthetics... but I like it nevertheless :joy_cat:

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[–] inaction_figure@fosstodon.org 1 points 4 weeks ago

@julian

Some really dislike switch. It's ok to like and use switch for its intended purpose, as long as you understand its idiosyncrasies.

Thanks for sharing this!

[–] nextgraph@fosstodon.org 1 points 4 weeks ago (1 children)

@julian so adding a && true at the end of your condition, should work, right?

case object && object.foo && true: {

[–] julian@community.nodebb.org 1 points 4 weeks ago

@nextgraph@fosstodon.org in my case, I just casted it as bool: !!object.foo. You could also object.hasOwnProperty('foo'), although that would be true if object.foo = null too :joy: