What is the best way to manage an empty JavaScript object?

Question

What is the best way to manage an empty JavaScript object?

I'm feeling stuck.

Check out this code snippet:

const clientInfoPromise = buildPromiseMethod
clientInfoPromise.then((clients) => {
    console.log('clients ' + JSON.stringify(clients))
    console.log(clients.typeOf)
    console.log(_.keys(clients))

This is the current output:

clients {}
undefined
['undefined']

I want to get an empty array when I use _.keys(clients), rather than getting an array with the string 'undefined'.

_.isEmpty(clients) ? [] : _.keys(clients)

doesn't seem to solve the issue, as _.isEmpty returns false.

This is where ClientInfoPromise is being defined:

static buildPromiseMethod(cids) {
    if (condition) {
        // fetch data
        const data = [data,data1,data2]
        return Promise.resolve(_.zipObject(cids, data));
    } else {
      const clients = _(cids)
        .indexBy()
        .mapValues(() => {
          return undefined; //contains empty data
        })
        .value();
      return Promise.resolve(clients);
    }
  }

The values for cids can be undefined, [], or [1,2,3] (an array of numbers).

javascript ecmascript-6 lodash

Answer 1

Answer №1

console.log(clients.typeOf)

If you want to determine the type of variable clients, use console.log(typeof clients).

console.log(_.keys(clients))
< ['undefined']

The output from _.key indicates that clients has only one key, labeled as "undefined". This particular key-value pair is likely excluded from stringify due to its undefined value, causing it to be skipped.

To view all properties, including those omitted by stringify, instead of

console.log('clients ' + JSON.stringify(clients))

you can use

console.log('clients', clients)

This will display all properties, even if their values are undefined according to stringify.

In your case, the observed behavior may stem from a flaw in buildPromiseMethod, resulting in a promise resolving to an object with a single key of "undefined" and an unserializable value. For example:

> clients = { undefined: undefined };
> console.log('clients ' + JSON.stringify(clients))
< clients {}

> console.log(_.keys(clients))
< ['undefined']

This aligns with what you've described experiencing.

The issue might originate from zipObject. Is this indeed the exact code snippet being executed? For instance, utilizing _.zipObject([cids], data) could lead to the reported outcome when cids is undefined and data contains undefined values:

var data, data1, data2;       // all values are undefined
data = [data, data1, data2];
var cids = undefined;
_.zipObject([cids], data);

> { undefined: undefined }

Moreover, it's plausible that mistakes are made regarding promises, especially if // fetch data occurs asynchronously. Consider adjusting the function as follows:

static buildPromiseMethod(cids) {
  if (condition) {
    return fetchdata().then(data => 
      _.zipObject(cids, data));
  }

This potential alteration could relate to the problem at hand, particularly if data1 etc. are delivered through the promise and accessed prematurely before completion, leading their values to be undefined.

Answer 2

console.log(clients.typeOf)

If you want to determine the type of variable clients, use console.log(typeof clients).

console.log(_.keys(clients))
< ['undefined']

The output from _.key indicates that clients has only one key, labeled as "undefined". This particular key-value pair is likely excluded from stringify due to its undefined value, causing it to be skipped.

To view all properties, including those omitted by stringify, instead of

console.log('clients ' + JSON.stringify(clients))

you can use

console.log('clients', clients)

This will display all properties, even if their values are undefined according to stringify.

In your case, the observed behavior may stem from a flaw in buildPromiseMethod, resulting in a promise resolving to an object with a single key of "undefined" and an unserializable value. For example:

> clients = { undefined: undefined };
> console.log('clients ' + JSON.stringify(clients))
< clients {}

> console.log(_.keys(clients))
< ['undefined']

This aligns with what you've described experiencing.

The issue might originate from zipObject. Is this indeed the exact code snippet being executed? For instance, utilizing _.zipObject([cids], data) could lead to the reported outcome when cids is undefined and data contains undefined values:

var data, data1, data2;       // all values are undefined
data = [data, data1, data2];
var cids = undefined;
_.zipObject([cids], data);

> { undefined: undefined }

Moreover, it's plausible that mistakes are made regarding promises, especially if // fetch data occurs asynchronously. Consider adjusting the function as follows:

static buildPromiseMethod(cids) {
  if (condition) {
    return fetchdata().then(data => 
      _.zipObject(cids, data));
  }

This potential alteration could relate to the problem at hand, particularly if data1 etc. are delivered through the promise and accessed prematurely before completion, leading their values to be undefined.

What is the best way to manage an empty JavaScript object?

Answer №1

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