Typescript access hashmap with string variable

Question

I made this simple code:

const testHashMap = {
    hello: "Hi",
    test: "Hey",
    blabla: "Halo"
}

const inputFromField : string = "hello";

alert(testHashMap[inputFromField]);

But the last line doesn't work because it demands that inputFromField will be from type "hello" | "test" | "blabla" and not a general string, how can I insist to use string? as it should be an input from the user in the future.

julianobrasil · Accepted Answer · 2020-04-15 08:53:21Z

1

You can explicitly declare the type for your constant:

const testHashMap: Record<string, string> = {
    hello: "Hi",
    test: "Hey",
    blabla: "Halo"
}

Record<string,string> is a more readeable form (syntactic sugar?) for {[key: string]: string}. You could have written the code above like this and it would mean the same:

const testHashMap: {[key: string]: string} = {
    hello: "Hi",
    test: "Hey",
    blabla: "Halo"
}

edited Apr 15, 2020 at 8:53

answered Apr 14, 2020 at 21:55

julianobrasil

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1 Comment

Dorki Over a year ago

Just from curiosity, could you show how it would be done without the Record interface?

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