Set First Value as Key in Javascript Array

Question

Creating an array based off selected DataTables Rows

$('#savenlp').click(recordjourney);

function recordjourney() {
var data = table.rows(['.selected']).data().toArray();
console.log( (data) );
console.log( JSON.stringify(data) );
}

data returns

0 : (8) ["Which", "TitleCase", "QuestionWord", "", "", "", "", ""]

JSON.stringify(data) returns

[["baseball","Noun","Singular","","","","",""]]

This information is dynamically generated, so I am just looking to take the first value (in this case baseball) and turn it into something like

  "baseball": [
    "Noun",
    "Singular"
  ]

I can return the first value (the key I want using)

alert(data[0][0]);

I am much more adept in PHP but I am learning javascript/jquery more and more.

It is my understanding javascript does not have associative arrays, so I am a bit confused as to how to generate this.

generalhenry · Accepted Answer · 2018-05-03 03:59:39Z

4

const data = [
  ["baseball","Noun","Singular","","","","",""],
  ["baseballs","Noun","","Plural","","","","",]
];
const mappedData = data.reduce((acc, row) => { acc[row.shift()] = row.filter(d => d !== ''); return acc; }, {});
console.log(mappedData);

edited May 3, 2018 at 3:59

answered May 3, 2018 at 3:36

generalhenry

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Comments

Prasanna · Accepted Answer · 2018-05-03 05:29:45Z

4

We can use object destructuring and spread operators for ease of use. In the example below, the key will be the first item and all the rest items will be placed in the newData variable

const data = [["baseball","Noun","Singular","","","","",""]];
const [key, ...newData] = data[0]
// if you want the new data to not have empty entries, simple apply the filter
const newDataFiltered = newData.filter(item => !!item)
const objWithEmpty = {[key]: newData}
const objWithoutEmpty = {[key]: newDataFiltered}


console.log(objWithEmpty, objWithoutEmpty)

For multiple arrays inside the outer array, just enclose the whole logic inside a for loop

const data = [
  ["baseball","Noun","Singular","","","","",""],
  ["baseball1","Noun1","Singular1","","","","",""],
  ["baseball2","Noun2","Singular2","","","","",""]
];
const objWithEmpty = {}
const objWithoutEmpty = {}

data.forEach((array) => {
  const [key, ...newData] = array
  // if you want the new data to not have empty entries, simple apply the filter
  const newDataFiltered = newData.filter(item => !!item)
  objWithEmpty[key] = newData
  objWithoutEmpty[key] = newDataFiltered
})

console.log(objWithEmpty, objWithoutEmpty)

edited May 3, 2018 at 5:29

answered May 3, 2018 at 3:37

Prasanna

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3 Comments

Brian Bruman Over a year ago

Lots of great answers but this one I am liking best! Thank you everyone.

Brian Bruman Over a year ago

Actually this one doesn't work with more than one array. @generalhenry one line answer now seems best.

Prasanna Over a year ago

@BrianBruman just enclosing the whole logic inside a forEach statement would solve your problem. That being said, the answer selected is indeed elegant :)

CertainPerformance · Accepted Answer · 2018-05-03 03:33:38Z

Simply extract the desired values from data and put them into an object formatted as you like:

const data = [["baseball","Noun","Singular","","","","",""]];
const firstArr = data[0];
const transformedFirstObject = {
  [firstArr[0]]: [firstArr[1], firstArr[2]],
};
console.log(transformedFirstObject);

But it's pretty weird to have an object with only one property like that. If your data might have more than one sub-array in it and you want to turn the array of arrays into an array of objects, use map:

const data = [
  ["baseball","Noun","Singular","","","","",""],
  ["foo","bar","baz","","","","",""]
];

const transformed = Object.assign(...data.map(([prop, value1, value2]) => ({ [prop]: [value1, value2] })));
console.log(transformed);

Sangram Nandkhile · Accepted Answer · 2018-05-04 00:53:03Z

2

A bit simpler compared to other answers here but works as well.

const data = [
  ["baseball","Noun","Singular","","","","",""],
  ["baseball1","Noun1","Singular1","","","","",""],
  ["baseball2","Noun2","Singular2","","","","",""]
];

const obj = [];
data.forEach(function(i) {
  let jsonObj = {};
  jsonObj [i[0]] = i.slice(1).filter(x=>x !='');
  obj.push(jsonObj)
});

console.log(JSON.stringify(obj))

edited May 4, 2018 at 0:53

answered May 3, 2018 at 3:49

Sangram Nandkhile

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2 Comments

Sachi Tekina Over a year ago

You should use j.slice(1, j.length).

Sangram Nandkhile Over a year ago

Actually, j.slice(1); would be more than sufficient :)

Sachi Tekina · Accepted Answer · 2018-05-03 04:00:43Z

1

Just using forEach, considering multiple array elements.

var obj = {};
var arr = [
  ["baseball", "Noun", "Singular", "", "", "", "", ""],
  ["Test", "Test1", "Test2", "", "", "", "", ""]
];

arr.forEach(function(val, idx) {
  val.forEach(function(val1, idx1) {
    if (idx1 === 0) {
      obj[val1] = val.slice(1, val.length)
    }
  })
})
console.log(JSON.stringify(obj))

answered May 3, 2018 at 4:00

Sachi Tekina

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