async and promise

async.js

//Mock card object
let card = {
  issueCommand: new Promise(function(resolve, reject) {
    resolve("issueCommand");
  })
}

//Mock ResponseApdu
class ResponseApdu {
    constructor(rawResponse) {
        this.rawResponse = rawResponse;
    }
}

//Option 1: Use promise (similar to issueCommand: https://github.com/tomkp/smartcard/blob/2373b010790aa11cf8e9df740c5dd1368a0aae25/src/Iso7816Application.js#L38-L63 )
let runCommandPromise = (card) => {
  return card.issueCommand.then( rawResponse => new ResponseApdu(rawResponse) )
}
runCommandPromise(card).then(response => console.log(response))

//Option 2: Declare function itself as async (which is interchangable with Promise)
let runCommandAsync = async (card) => {
    let rawResponse = await card.issueCommand;
    return new ResponseApdu(rawResponse);
}  

runCommandAsync(card).then(response => console.log(response)); //Use as Promise

//Or use as async function in someother function
async function someOtherFn(card) {
    return await runCommandAsync(card);
}