Javascript: How to find key name in array of objects [duplicate]

Question

I am trying to determine if a key name is present in my array of object. As an example, how would I verify if the key with a name of 'name' equals the argument passed in my function call? Below is code to further clarify.

var stooges = [{name: 'moe', age: 40}, {name: 'larry', age: 50}, {name: 'curly', age: 60}];
var test = function(arr, propName){
var result = [];
for(var i = 0; i < arr.length; i++){
    if(arr[i][propName] === propName){
        result.push(arr[i][propName]);
    }
}
return result;
} 
func(stooges, "name");

If you only want to test the presence of the property, you can do if (propName in arr[i]) or if (arr[i].hasOwnProperty(propName). Is that what you want? arr[i][propName] === propName compares the value of the property with its name, which would only be true if you had name: "name" (which would be odd). — Felix Kling
– Felix Kling, Commented Apr 28, 2015 at 23:52
@Malk I expect test(stooges, "name") to return => ["moe", "larry", "curly"] — Chris Smith
– Chris Smith, Commented Apr 28, 2015 at 23:57
@TitoEsteves that is explicitly not what your question text asks for. — Alnitak
– Alnitak, Commented Apr 28, 2015 at 23:57

Alnitak · Accepted Answer · 2015-04-29 00:10:41Z

0

Using underscore.js:

var names = _.pluck(stooges, 'name');

In fact this is the very example given on their page?!

So, on the basis that you knew this, but want to know how to write something similar:

function pluck(array, prop]) {
    return array.map(function(entry) {
        return entry[prop];
    });
}

or more safely, returning an empty array if the initial array is undefined:

function pluck(array, prop]) {
    return array ? array.map(function(entry) {
        return entry[prop];
    }) : [];
}

edited Apr 29, 2015 at 0:10

answered Apr 28, 2015 at 23:57

Alnitak

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3 Comments

Chris Smith Over a year ago

Yes I am trying to write my own version of the underscore pluck function. I feel it is good practicing. Thanks

Alnitak Over a year ago

@TitoEsteves I've included that too. You could, of course, have just read the source code for underscore...

Chris Smith Over a year ago

I did not comprehend that. That is far more advanced then the solution I came up with. Still new to programming.

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