Efficient way to find name value pairs from JSON array in Javascript

Question

I am currently making a call to a service which sends a response as an array of objects with name value pairs. An example of this can be seen below. There could be any amount of these name value pairs in any order but I just want to access the value for the name "name2". Is there an efficient way other than looping through each object and checking the name to obtain the corresponding value for name2?

[{"name":"name1","value":"value1"},{"name":"name2","value":"value2"}]

So from the above data set I would want an efficient way to search for name2 and get the corresponding value "value2".

Thanks

efficient way other than looping No. Any mechanism will use loop internally — Rajesh Dixit
– Rajesh Dixit, Commented Dec 12, 2017 at 13:35
@Satpal for efficiency, I would rather suggest using for + if + break or for + return — Rajesh Dixit
– Rajesh Dixit, Commented Dec 12, 2017 at 13:35
If only needing a single record from the results is a common use case, you should probably get in touch with the service providing the results - they may be happy to update things at their end to filter the results to send less data to their users. — James Thorpe
– James Thorpe, Commented Dec 12, 2017 at 13:39

scunliffe · Accepted Answer · 2017-12-12 13:37:15Z

3

Unless you know the specific index of the object with the name name2 no.

You'll need to iterate until you find that name then you can bail out.

e.g.

var jsonData = [{"name":"name1","value":"value1"},{"name":"name2","value":"value2"}];
for(var i=0;i<jsonData.length;i++){
  if(jsonData[i]['name'] == 'name2'){
    console.log('The value is: ' + jsonData[i]['value']);
    break;
  }
}

Note that if you don't need to support Internet Explorer, you can use the Array.find() method to simplify this.

answered Dec 12, 2017 at 13:37

scunliffe

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1 Comment

Rajesh Dixit Over a year ago

Should we not look and close it as dupe?

mina sameh · Accepted Answer · 2017-12-12 13:50:46Z

2

if you don't want to iterate over the array manually you can use lambda expression as the following

a =[{"name":"name1","value":"value1"},{"name":"name2","value":"value2"}] ;

//get the items that match your criteria 
a.filter(item=>item.name=="name2")

//get those items' values
a.filter(item=>item.name=="name2").map(item=>item.value)

//get the first value (if you know that it's only one item that will match)
a.filter(item=>item.name=="name2").map(item=>item.value)[0]

answered Dec 12, 2017 at 13:50

mina sameh

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Comments

2 revs · Accepted Answer · 2017-12-12 13:38:26Z

1

You can use Array#find method.

var arr = [{
  "name": "name1",
  "value": "value1"
}, {
  "name": "name2",
  "value": "value2"
}];

// get the object containing name as `name2`
var obj = arr.find(function(v) {
  return v.name === 'name2';
});

// get value property if object is defined
var res = obj && obj.value;

console.log(res)

edited Dec 12, 2017 at 13:38

community wiki

2 revs
Pranav C Balan

1 Comment

Rajesh Dixit Over a year ago

Should we not look and close it as dupe?

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