Get function parameter from key in array of objects - Typescript

Question

I have a function which takes an argument called functionName. functionName should always be the value of "Name" property from an array of objects. I skimmed through this but I was not able to achieve what I am looking for.

This is what I have.

const data = [{
  Name: 'functionA',
  EntryPoint: false,
  SystemOrClient: 'Client'
}, {
  Name: 'functionB',
  EntryPoint: false,
  SystemOrClient: 'Client'
}, {
  Name: 'functionC',
  EntryPoint: false,
  SystemOrClient: 'System'
}] as const;

const getSystemInfo = (functionName: string) => { //functionName should only accept values of Name property
//...
}


getSystemInfo('functionA') //should pass
getSystemInfo('functionAB') //should fail while compiling

Please help.

Tobias S. · Accepted Answer · 2022-07-22 16:10:19Z

2

You can get the type of data with the typeof operator. This can be indexed with number to get a union of all elements which you can index with the Name property.

const getSystemInfo = (functionName: typeof data[number]["Name"]) => {}

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answered Jul 22, 2022 at 16:10

Tobias S.

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2 Comments

arunmmanoharan Over a year ago

Thanks. How do I still enforce an interface to the array of objects? I did readonly IData[] which converts the name to a string.

Tobias S. Over a year ago

If you give data an explicit type, all information about the actual object you assigned to it will be lost. The only option is having a no-op generic function just for initialising the object.

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