Extracting single key from object to array

Question

I'm looking at extracting keys from an Object and push them to an array in Javascript (Nodejs). An example would be:

var obj = [{tag: 'ft001', addr: 'DB415.DBD2'}, {tag: 'ft001', addr: 'DB415.DBD6'}];

function extractKey(arr, keyName) { 

// Result: ['ft001', 'ft002'];

}

How would I go about doing this?

have you tried `forEach` or `map` functions? – RomanPerekhrest Feb 14 '16 at 20:32 — RomanPerekhrest, Feb 14 '16 at 20:32
`var keys = obj.map(function(x) {return x.tag});` – adeneo Feb 14 '16 at 20:37 — adeneo, Feb 14 '16 at 20:37
Something like `obj.map(o=>o.tag)` should go close. – RobG Feb 14 '16 at 20:38 — RobG, Feb 14 '16 at 20:38

score 1 · Answer 1 · answered Feb 14 '16 at 20:35

if a typo [ 'ft001', 'ft002'], then the following would you be useful:

function extractKey() {
    var result = [];
    for (var index = 0; index < obj.length; index++) {
        result.push(obj[index].tag);        
    }
    return result;
// Result: ['ft001', 'ft001'];
}

score 1 · Accepted Answer · answered Feb 14 '16 at 20:38

1

Use Array.prototype.map():

var obj = [{tag: 'ft001', addr: 'DB415.DBD2'}, {tag: 'ft001', addr: 'DB415.DBD6'}];

function extractKey(arr, keyName) { 
  return arr.map(x=> x[keyName])
}

I think it's rather self-explaining.

answered Feb 14 '16 at 20:38

Michał Perłakowski

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Extracting single key from object to array

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