How retrieve json element by key (Javascript)

Question

I would like to retrieve option with key '2021-05-14' from this json-object.

{
  stock: {
    zip: '95014',
    lastUpdated: '05/02/2021'
  },
  options: [
    { '2021-05-07': [Object] },
    { '2021-05-14': [Object] },
    { '2021-05-21': [Object] },
    { '2021-05-28': [Object] },
    { '2021-06-04': [Object] },
    { '2021-06-18': [Object] }
  ]
}

I tried:

var options;
var expirationSeries;
options = res.body.options;  // res.body is the json-object
for (var key in options)
{
  if (key=='2021-05-14') {
    expirationSeries = options[key];
  };
}
console.log(expirationSeries);

but then I get error 'undefined'.

How to do this properly?

Did you debug your code or add console.log(key) to see what it returns? You need to loop through the array and check if each object has the key '2021-05-14' — adiga
– adiga, Commented May 2, 2021 at 13:31
it's seems like your JSON options is array of json objects so key is a number, not a date as you mention above. — assaf.b
– assaf.b, Commented May 2, 2021 at 13:32
This can be done in several ways, but maybe with a slight change in your code this could even be simpler. If the order of your options collection is not important, you could turn this into an object instead of an array, and simply have options{'2021-05-07': [Object],'2021-05-14': [Object],'2021-05-21': [Object]}, achieving what you want to do simply using options['2021-05-14'] — Laurent S.
– Laurent S., Commented May 2, 2021 at 13:32
Use console.log to see what you're getting. Note that for (var k in ["first", "second"]) { will give 0, 1 so I think you'll find that key is a number. — user2740650
– user2740650, Commented May 2, 2021 at 13:33

AnthonyTonev · Accepted Answer · 2021-05-02 13:44:54Z

2

Since options is an array you can use find to get the first object that has a property key in it.

const jsonData = {
  stock: {
    zip: '95014',
    lastUpdated: '05/02/2021'
  },
  options: [
    { '2021-05-07': {} },
    { '2021-05-14': {} },
    { '2021-05-21': {} },
    { '2021-05-28': {} },
    { '2021-06-04': {} },
    { '2021-06-18': {} }
  ]
 }

const key = '2021-05-21';

const result = jsonData.options.find(option => key in option );

console.log(result)

answered May 2, 2021 at 13:44

AnthonyTonev

211 silver badge3 bronze badges

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

Comments

adiga · Accepted Answer · 2021-05-02 13:47:43Z

Using for (var key in options) over an array will assign the indices of the array to key variable.

You could use for..of loop and use hasOwnProperty to check if the object has that date as property. Since you want only one match, you could break if a match is found

for (const o of options) {
  if (o.hasOwnProperty('2021-05-14')) {
    expirationSeries = o
    break;
  }
}

Here's a snippet:

let options = [{"2021-05-07":{foo:"bar"}},{"2021-05-14":{foo:"bar"}},{"2021-05-21":{foo:"bar"}},{"2021-05-28":{foo:"bar"}},{"2021-06-04":{foo:"bar"}},{"2021-06-18":{foo:"bar"}}],
    expirationSeries;
  
for (const o of options) {
  if (o.hasOwnProperty('2021-05-14')) {
    expirationSeries = o
    break;
  }
}

console.log(expirationSeries)

You could use find and hasOwnProperty to get the object which has the specified key. If multiple objects can have that key, use filter to get all the matches

const expirationSeries = options.find(a => a.hasOwnProperty('2021-05-21'))
const allMatches = options.filter(a => a.hasOwnProperty('2021-05-21'))

Here's a snippet:

const options = [{"2021-05-07":{foo:"bar"}},{"2021-05-14":{foo:"bar"}},{"2021-05-21":{foo:"bar"}},{"2021-05-28":{foo:"bar"}},{"2021-06-04":{foo:"bar"}},{"2021-06-18":{foo:"bar"}}],
    expirationSeries = options.find(a => a.hasOwnProperty('2021-05-21')),
    allMatches = options.filter(a => a.hasOwnProperty('2021-05-21'))

console.log(expirationSeries)
console.log(allMatches)

benada002 · Accepted Answer · 2021-05-02 13:39:01Z

1

You could also try this:

options.forEach(obj => {
  const key = Object.keys(obj)[0];

  if (key == '2021-05-14') {
    expirationSeries = options[key];
  };
});

answered May 2, 2021 at 13:39

benada002

2911 gold badge2 silver badges8 bronze badges

Comments

KooiInc · Accepted Answer · 2021-05-02 13:45:59Z

1

You can use Array.find to find the object within the options array. Something like:

const fromJson = {
  stock: {
    zip: '95014',
    lastUpdated: '05/02/2021'
  },
  options: [
    { '2021-05-07': {} },
    { '2021-05-14': {} },
    { '2021-05-21': {} },
    { '2021-05-28': {} },
    { '2021-06-04': {} },
    { '2021-06-18': {} },
  ]
}

const expirationSeries = findOptionByKey(`2021-05-14`);
console.log(expirationSeries);

// not found
console.log(findOptionByKey(`2022-03-12`));


function findOptionByKey(key2Find) {
  const keyFinder = obj => obj[key2Find];
  return fromJson.options.find(keyFinder) || `option [${key2Find}] not found`;
}

answered May 2, 2021 at 13:45

KooiInc

124k32 gold badges145 silver badges181 bronze badges

Comments

Mamun · Accepted Answer · 2021-05-02 13:46:47Z

Instead of for...in you can try using for...of.

Demo:

var options;
var expirationSeries;
options = [
    { '2021-05-07': 'data 1' },
    { '2021-05-14': 'data 2' },
    { '2021-05-21': 'data 3' },
    { '2021-05-28': 'data 4' },
    { '2021-06-04': 'data 5' },
    { '2021-06-18': 'data 6' }
  ]
for (var obj of options)
{
  var k = Object.keys(obj)[0];
  if (k=='2021-05-14') {
    expirationSeries = obj[k];
  };
}
console.log(expirationSeries);

OR: You can try using .find()

var options = [
    { '2021-05-07': 'data 1' },
    { '2021-05-14': 'data 2' },
    { '2021-05-21': 'data 3' },
    { '2021-05-28': 'data 4' },
    { '2021-06-04': 'data 5' },
    { '2021-06-18': 'data 6' }
  ];
var temp = options.find(o => Object.keys(o)[0] === '2021-05-14');
var expirationSeries =  temp != undefined ? Object.values(temp)[0] : 'not found';
console.log(expirationSeries);

Collectives™ on Stack Overflow

How retrieve json element by key (Javascript)

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related