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MOHSIN ALI SOOMRO
MOHSIN ALI SOOMRO

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Prefer more precise alternative to the string Types in Typescript

The domain of string type is big

Suppose you're building music collection and you want to define a type for an album

Attemp:

interface Album{
 artist:string;
 title:string;
 releaseDate:string; //YYYY-MM-DD
 recordingType:string; // "live" or "studio"
}
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The prevelance of string types and the type information in comments are strong indications that this interface isn't quite right. Here is what can go wrong.

const kindOfBlue:Album ={
 artist:"Miles Devid",
 title:"Kind of blue",
 releaseDate:"auguest 17th 1959",
 recordingType:"Studio",
}
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Problem 1:
Date is not formated
Problem 2:
recordingType Studio is small spell but it is capital.

How to narrow down string and solve these problem?

type RecordingType="studio" | "live" 
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interface Album{
 artist:string;
 title:string;
 releaseDate:Date; 
 recordingType:RecordingType; 
}
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const kindOfBlue:Album ={
 artist:"Miles Devid",
 title:"Kind of blue",
 releaseDate:new Date("1959-08-18"),
 recordingType:"studio",
}
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With these changes Typescript is able to do a more thorough check for errors

Make more precise type to error pron the code.

Thanks.

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