How can I extract some data from a array of dict to put in a array?

Question

I am trying to extract some data from an array of dict but it does not work...

Here is my code :

var myarray = [{'country': 'US', 'type': 'eat'}, {'country': 'DE', 'type': 'test'}]

var arr = []
for (var key in myarray){
if (key.hasOwnProperty('country')){
        arr.push(key.country)
    }
}
console.log(arr);

What I want at the end is this arr = ['US', 'DE']

I precise I am using React.js maybe there is a function more efficient to do that ... but I did not found...

Here is my code : http://jsfiddle.net/n3o61bcw/

Thank you a lot for your help !

Or Assayag · Accepted Answer · 2020-11-28 19:21:50Z

2

var myarray = [{'country': 'US', 'type': 'eat'}, {'country': 'DE', 'type': 'test'}];
const arr = myarray.map(c => c.country);

answered Nov 28, 2020 at 19:21

Or Assayag

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Comments

lawrence-witt · Accepted Answer · 2020-12-06 23:54:08Z

2

The reason your code doesn't work is that the iterable key of an array is just its index. So you're checking whether 0.hasOwnProperty('country') e.t.c. which obviously doesn't make sense. You could fix this by doing:

if (myarray[key].hasOwnProperty('country')){
        arr.push(myarray[key].country)
    }
}

But it makes more sense to reduce the array instead:

const arr = myarray.reduce((a, c) => a.concat(c.country || []), []);

edited Dec 6, 2020 at 23:54

answered Nov 28, 2020 at 19:26

lawrence-witt

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Comments

Yves Kipondo · Accepted Answer · 2020-11-28 20:35:12Z

What you want to achieve isn't related to React specifically, It can be done using javascript functionality. On the other hand, you want to return the value of the specific key of each object inside of myarray

You can perform that using Array.prototype.reduce method like this

let myArray = [
  {'country': 'US', 'type': 'eat'}, 
  {'country': 'DE', 'type': 'test'}
];

const result = myArray.reduce((accumulator, current) => {
  return accumulator.concat(current.country);
}, []);

console.log(result);

of using Array.prototype.map like this

let myArray = [
  {'country': 'US', 'type': 'eat'}, 
  {'country': 'DE', 'type': 'test'}
];

const result = myArray.map(item => {
  return item.country;
});

console.log(result);

There many way to achieve the same result

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