JavaScript - Flatten Array of Nested Objects

Question

I am working with an array of objects and need to flatten and re-assign the data set into an array of single objects using the object values as the new object keys.

Incoming Data:

results = [
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Jim' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Fredsburg' },
    ],
  },
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Greg' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Waverly' },
    ],
  },
];

Desired Result:

output = [
  {
    id: 1, FirstName: 'Jim', LastName: 'Jones', City: 'Fredsburg',
  },
  {
    id: 2, FirstName: 'Greg', LastName: 'Jones', City: 'Waverly',
  },
];

My current attempt gets me to placing the updated key/value pairs in the correct order, but creates a huge array of single objects.

Current Code:

const results = [];

surveyResults.map(s => s.surveyValues)
  .forEach(s => Object.entries(s)
  .forEach(([key, value]) => {
    Object.entries(value)
      .forEach(([k, v]) => {
        if (k === 'name') {
          results.push({
            id: value.id,
            [v]: value.value.toString(),
          });
        }
    });
}));

Current Code Output:

[
  {
    id: 135, FirstName: 'Jim',
  },
  {
    id: 136, LastName: 'Jones',
  },
  {
    id: 137, City: 'Fredsburg',
  },
  {
    id: 135, FirstName: 'Greg',
  },
  {
    id: 136, LastName: 'Jones',
  },
  {
    id: 137, City: 'Waverly',
  },
]

What am I missing and why is my code not created the new arrays of objects as desired?

ggorlen · Accepted Answer · 2018-08-25 01:13:36Z

2

You may use map and reduce to accomplish this. I'm also accessing an index i in the map function's callback to set the id property and string.replace() to strip the space from the FirstName and LastName keys.

const results = [
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Jim' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Fredsburg' },
    ],
  },
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Greg' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Waverly' },
    ],
  },
];


const result = results.map((e, i) => 
  e.surveyValues.reduce((a, e) => {
    a[e.name.replace(" ", "")] = e.value;
    return a;
  }, {id: i + 1})
);

console.log(result);

edited Aug 25, 2018 at 1:13

answered Aug 24, 2018 at 22:41

ggorlen

59.3k8 gold badges119 silver badges173 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Barmar · Accepted Answer · 2018-08-24 22:45:42Z

Create each object in the outer map() loop, and add properties to it in the inner forEach().

surveyResults = [
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Jim' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Fredsburg' },
    ],
  },
  {
    surveyValues: [
      { id: 135, name: 'First Name', value: 'Greg' },
      { id: 136, name: 'Last Name', value: 'Jones' },
      { id: 137, name: 'City', value: 'Waverly' },
    ],
  },
];

const results = surveyResults.map((s, i) => {
  let v = s.surveyValues;
  let obj = {id: i};
  v.forEach(item => obj[item.name.replace(/\s+/g, "")] = item.value.toString());
  return obj;
});

console.log(results);

Collectives™ on Stack Overflow

JavaScript - Flatten Array of Nested Objects

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related