Object entries returning undefined

Question

I have a json object returned from a SQL query. I want to filter out the json key before sending back to the front end. If the key is true, return back to the front end is what I am looking for.

In my server file I have this line.

          let returned_data = Object.entries(queried_data[0]).forEach((key, value) => {
            return value === true ? key : null
          })
          res.json(returned_data)

This is an example of my returned json after SQL querying.

[{first_name: 'testing', has_apple: true, has_pear: true, has_beans: false}]

I am expecting the returned_data to have ['has_apple', 'has_pear']. Right now I am getting undefined for returned_data

`Object.entries()` never returns `undefined`. `forEach` always does. — Bergi, Feb 21 '19 at 19:38
Are you positive you aren't required to perform a JSON operation on `queried_data` prior to interacting with it with `Object`? — theaccordance, Feb 21 '19 at 19:39
@theaccordance You are right, I can see something is not right from the console.log, after changing from `forEach` to `map` I am getting a messed up output. I need to see which JSON operation I will need to do. — calvert, Feb 21 '19 at 19:44

score 4 · Accepted Answer · answered Feb 21 '19 at 19:39

4

forEach doesn't return anything map does. Also Object.entries returns an array of arrays and hence you need to destructure the value in map function to get key and value. Change your code to

      let returned_data = Object.entries(queried_data[0]).map(([key, value]) => {
        return value === true ? key : null
      })
      res.json(returned_data)

answered Feb 21 '19 at 19:39

Shubham Khatri

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Thank you. I am getting something in the return. – calvert Feb 21 '19 at 19:54

score 1 · Answer 2 · answered Feb 21 '19 at 19:49

1

As other answers say forEach() doesn’t return anything so either you have to use map() or create an array and push value to it if true

var new_data=[];
Object.entries(queried_data[0]).forEach((key, value) => {
       if( value===true){new_data.push(key)}
});
console.log(new_data);

answered Feb 21 '19 at 19:49

Osama

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This gives exactly what I wanted for the result. I will try out others' solutions too for knowledge. Thank you. – calvert Feb 21 '19 at 19:54

score 0 · Answer 3 · answered Feb 21 '19 at 19:41

I think you are looking for

const returned_data = Object.entries(queried_data[0]).map((key, value) => {
    return value === true ? key : null
}).filter(key => {
    return key !== null
});

or simply

const returned_data = Object.keys(queried_data[0]).filter(key, queried_data[0][key] === true);

Don't use forEach!

Object entries returning undefined

3 Answers3