DefinitelyTyped/types/vfile

VFile typescript Docs

Below are some examples of how to use these Definitions.
Scenarios where the Typescript code is identical to plain Javascript code are omitted.

Using data property

Because data property type is set unknown, you have to make your own type guard.

interface CustomData {
    message: string;
}
// This is the type guard
function isCustomData(data: any): data is CustomData {
    return data != null && typeof data.message === 'string';
}
function doSomethingWithCustomData(data: CustomData) {
}
const customData: CustomData = {
    message: 'tango'
};
const fileWithData = vfile({
    data: customData
});

if (isCustomData(fileWithData.data)) {
    doSomethingWithCustomData(fileWithData.data);
}
// The below code will throw a compiler error
doSomethingWithCustomData(fileWithData.data); // $ExpectError

Extending VFile

import vfile = require('vfile')

// 1. Define extended vfile interface
interface CustomVFile extends vfile.VFile {
    custom: string;
    data: {
        custom: number;
    };
}

// 2. Provide the extended interface to generic type parameter
// So it can be used for return value
const file: CustomVFile = vfile<CustomVFile>({
    path: '~/example.txt',
    contents: 'Alpha *braavo* charlie.',
    custom: 'Custom tango',
    data: {
        custom: 12345
    }
});

// vfile recognize extended VFile values. So it will return same type.
const copiedFile: CustomVFile = vfile(file);