How to turn an list of object into an array of objects in javascript?

Question

I'm learning to manipulate arrays and objects in Javascript.

This is a list of Objects:

Input:

{ user_id: 1,
  name: 'Alice',
  created_at: 2018-11-23T20:47:39.618Z,
  count: '3' }
{ user_id: 4,
  name: 'Daphne',
  created_at: 2018-11-19T21:47:39.618Z,
  count: '3' }
{ user_id: 2,
  name: 'Bob',
  created_at: 2018-11-23T18:47:39.618Z,
  count: '2' }
{ user_id: 5,
  name: 'Evan',
  created_at: 2018-11-18T19:47:39.618Z,
  count: '2' }
{ user_id: 6,
  name: 'Fabia',
  created_at: 2018-11-22T23:47:39.618Z,
  count: '2' }

Desired Output:

[ { user_id: 1,
    name: 'Alice',
    created_at: 2018-11-23T20:47:39.618Z,
    count: '3' },
  { user_id: 4,
    name: 'Daphne',
    created_at: 2018-11-19T21:47:39.618Z,
    count: '3' },
  { user_id: 2,
    name: 'Bob',
    created_at: 2018-11-23T18:47:39.618Z,
    count: '2' },
  { user_id: 5,
    name: 'Evan',
    created_at: 2018-11-18T19:47:39.618Z,
    count: '2' },
  { user_id: 6,
    name: 'Fabia',
    created_at: 2018-11-22T23:47:39.618Z,
    count: '2' } ]

I'm new to javascript programming. been trying to solve this problem but no solution yet? Anyone, please help?

Your list of objects is just "floating" in space, its not valid... — Nick Parsons
– Nick Parsons, Commented Nov 25, 2018 at 9:50
There is not such thing as a (built-in) list data type in JS. What do you mean with list? — trincot
– trincot, Commented Nov 25, 2018 at 9:54
The way you have presented that query result is not valid JS. Please show whether it is an object (with properties) or an array. Also show what you mean with destructuring it (into what?). To be sure, output JSON.stringify(queryresult) and put that in your question. — trincot
– trincot, Commented Nov 25, 2018 at 10:34

aquiseb · Accepted Answer · 2018-11-25 13:11:44Z

You should get it as JSON out of postgres with row_to_json(), json_agg and/or array_to_json(). See this documentation about Aggregate functions

select array_to_json(array_agg(row_to_json(t)))
from (
  select id, text from words
) t

Or, your list has to be a string as it is not valid JS.

`${yourQueryData}`

If the input has to be as mentioned in the question, so a string, (let's say from a txt input or whatever) here's what we can do.

We'll add brackets around that string to get started.

Then we identify each aspect that will not be valid when we parse it to JSON data.

Add commas between objects: }{ to },{
Get the keys and add quotes around them: user_id: to "user_id":
Replace single quotes by double quotes: 'Alice' becomes "Alice"
Your timestamps must be converted to strings: 2018-11-23T20:47:39.618Z to "2018-11-23T20:47:39.618Z"

Once this is all fixed, we use JSON.parse() and there you have your JSON array of objects.

There are many ways to get there. You could split your string at several places then iterate and do the necessary tasks.

Here I'll be using regex. For the sake of clarity, each step is quite explicit, even the regexes have way more groups than necessary but I hope it makes it easier to understand as it is.

This answer is based exactly on the code you provided. But it will require some modifications if a name containes a single quote for instance.

const list = `
{ user_id: 1,
  name: 'Alice',
  created_at: 2018-11-23T20:47:39.618Z,
  count: '3' }
{ user_id: 4,
  name: 'Daphne',
  created_at: 2018-11-19T21:47:39.618Z,
  count: '3' }
{ user_id: 2,
  name: 'Bob',
  created_at: 2018-11-23T18:47:39.618Z,
  count: '2' }
{ user_id: 5,
  name: 'Evan',
  created_at: 2018-11-18T19:47:39.618Z,
  count: '2' }
{ user_id: 6,
  name: 'Fabia',
  created_at: 2018-11-22T23:47:39.618Z,
  count: '2' }
`

// Add brackets around the list to have the string representation of an array
const array = `[${list}]` // wrap into array

// 1. Add commas between objects: `}{` to `},{`
const regex = /\}[\r\n|\r|\n]?\{/gm // match closing followed by opening bracket 
const fixObjects = array.replace(regex, "},\n{") // add comma at the end of each object

// 2. Get the keys and add quotes around them: `user_id:` to `"user_id":`
const keysReg = /^(?:[\s|\{]+)([\w]+)(?:\:)/gm // get keys
const fixKeys = fixObjects.replace(keysReg, function(match, g1) { return match.replace(g1, `"${g1}"`) }); // wrap keys in quotes

// 3. Replace single quotes by double quotes: `'Alice'` becomes `"Alice"`
const quotesReg = /'(.*)'/gm // match between single quotes
const fixQuotes = fixKeys.replace(quotesReg, function(match, g1) { return `"${g1}"` })

// 4. Your timestamps must be converted to strings: `2018-11-23T20:47:39.618Z` to `"2018-11-23T20:47:39.618Z"`
const datesReg = /(\d{4})\-(\d{2})\-(\d{2})T(\d{2}):(\d{2}):(\d{2}).(\d{3})Z/gm // timestamps as strings
const fixDates = fixQuotes.replace(datesReg, function(match) { return `"${match}"` } )

console.log(JSON.parse(fixDates))

oetoni · Accepted Answer · 2018-11-25 09:55:20Z

1

Also,

Object.values(obj);

where obj = your data

answered Nov 25, 2018 at 9:55

oetoni

4,0076 gold badges22 silver badges36 bronze badges

Comments

PretorDH · Accepted Answer · 2018-11-25 09:54:11Z

0

Try this..

objectsArray = Array.from( ObjectsList );

answered Nov 25, 2018 at 9:54

PretorDH

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