A better way to doing if statements in javascript #shorts

Instead of using a large if statement block to set a variable, try using a lookup map instead in javascript.

#shorts

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[yx]

beware that objects created with object literals inherit properties from Object.prototype . that means that if day is 'toString', then values[day] will actually return a function and not a numerical value as you expect

[elatedbento]

This is an interesting approach not just for JavaScript. Maps are everywhere. Thanks for sharing.

[goranjosic]

The beauty of Python is that you learn these things at the very beginning, because in python this approach is taken for granted. That's my experience.

[AnyVideo]

Nice, I too prefer this method. Howell, in the case of numerical keyed data, the array is a much better fit paired with an indexOf or findIndex

[eugenb]

Wow, you "invented" the dictionary. Great job!

[jaydeepkarena]

have used this so many times.... very useful

[changalex]

In this case I will use an array with string + indexOf

[matheuslopesmarques]

const values = ['tuesday', 'monday', 'wednesday']
values.indexOf('tuesday') // return 0
values.indexOf('sunday') // return -1 becausa not exist

[Aeyzaz]

A different approach would be an Array and just find the index

[dominikmatis]

const arr = ['monday', ….]
const day = arr.indexOf('monday')

[jofetgc]

Everyone commenting saying "I would just indexOf()... array... List...etc" doesn't understand that this is incredibly useful for data that is non continuous and works for reference types as well. The only reason this works is because Mon-Sun is linearly mapped to 0-7.

Im a C# dev and we call them dictionaries instead of maps but essentially they are a collection of key->value pairs, where the values could even be generic in type. The last implementation I used this for was in a 'inventory' system (game dev). I can't recall why I needed a dictionary instead of just a list, but they are incredibly useful structures for representing data in all sorts of ways.

[SirDamatoIII]

One line:
return [“monday”, ”…].IndexOf(day);

[charliesta.abc]

Good tip. If you need to do anything more than this with maps, use the Map type.

[andyvu]

For a string mapping, I usually do things like

const childTheme = {
white: ‘black’,
…
}[parentTheme]

By setting parentTheme default to ‘white’, the default for childTheme will always be ‘black’.

[Rudxain]

When dealing with arbitrary data, it's better to use an actual `Map` than an object, for the same reason the top comment mentioned (prototype collision). Or just use an Object stripped off its prototype

[BboyHotshot]

switch-case works great here as well. Switch only evaluates once, while if-else evaluates for every condition set...and you don't have to store anything. Best performance as well as storage utilization.

[StuartAylward]

Or you could literary use Map followed by nullish coalescing ...

days = new Map([...])
days.get(day) ?? -1

[stianscholtz]

Just make an array and use indexOf. Even simpler.

[froxx]

When you do it in typescript and define its type like Record<Day, number> you can even save the fallback value since typescript will prevent you to pass in any possible value other than Day (which you would have to define as a literal chain as well like "type Day = 'monday' | 'tuesday'..."

[rickvian]

as js professional, i can cofirm this is what i do all the time, please do this folks

but keep in mind about accessing property of null it can crash on run time

in this video, he use bracket notation rather than dot notation, it makes difference