_.pick method to match the sub property in an objects array

Question

I am using _.pick method in the following manner

suppose I have an array of strings which are nothing but property names I want to get from each object in array of objects

var wantedPropArray=["prop1","prop2","prop3.name"];

Below is my objects array

var objectArray = [
        {"prop1":"prop1Data1","prop2":"prop2Data1","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data1","prop5":"prop5Data1"},
        {"prop1":"prop1Data2","prop2":"prop2Data2","prop3":{"name":"Cat","age":"24","class":"graduate"},"prop4":"prop4Data2","prop5":"prop5Data2"}
        {"prop1":"prop1Data3","prop2":"prop2Data3","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data3","prop5":"prop5Data3"}
        {"prop1":"prop1Data4","prop2":"prop2Data4","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data4","prop5":"prop5Data4"}
    ]
for( var item in objectArray ){          
    var objectArrayOnlySelectedProperties = _.pick(objectArray[item] , wantedPropArray);
}

suppose for first iteration lets see objectArrayOnlySelectedProperties data, I am getting

objectArrayOnlySelectedProperties = {"prop1":"prop1Data1","prop2":"prop2Data1"};

I am expecting it to give me the result something like this

objectArrayOnlySelectedProperties = {"prop1":"prop1Data1","prop2":"prop2Data1","prop3.name":"Tom"};

what i mean to say is _.pick method is not able to look into prop3 and get me prop3.name. Can anyone suggest how to use underscores' pick method to match the sub properties of each object in an array.

Thanks in advance

Mike Hogan · Accepted Answer · 2013-03-05 15:12:01Z

3

It looks like this is not supported with underscorejs out of the box. But there is this gist that offers the support as a mix-in:

https://gist.github.com/furf/3208381

Here is some code using the above gist to do what you need: http://jsfiddle.net/wHXCv/1/

_.mixin({
  deep: function (obj, key) {
    var keys = key.split('.'),
        i = 0,
        value = null,
        n = keys.length;

      while ((obj = obj[keys[i++]]) != null && i < n) {};
      value = i < n ? void 0 : obj;
      var result = {};
      result[key]=value;
      return result;
  }
});

var objectArray = [
                 {"prop1":"prop1Data1","prop2":"prop2Data1","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data1","prop5":"prop5Data1"},
                 {"prop1":"prop1Data2","prop2":"prop2Data2","prop3":{"name":"Cat","age":"24","class":"graduate"},"prop4":"prop4Data2","prop5":"prop5Data2"},
                 {"prop1":"prop1Data3","prop2":"prop2Data3","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data3","prop5":"prop5Data3"},
                 {"prop1":"prop1Data4","prop2":"prop2Data4","prop3":{"name":"Tom","age":"24","class":"graduate"},"prop4":"prop4Data4","prop5":"prop5Data4"}];

var plucked = function(o, wantedPropArray) {
    return _.reduce(wantedPropArray, function(acc, val){
        acc.push(_.deep(o,val));
        return acc;
    },[]);
}

var answer = _.map(objectArray, function(o){
    return plucked(o, ["prop1","prop2","prop3.name"]);
});

console.log(JSON.stringify(answer));

edited Mar 5, 2013 at 15:12

answered Mar 5, 2013 at 11:28

Mike Hogan

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8 Comments

bhargav Over a year ago

the links you gave are good,but is it possible that i can get both the keys and values instead of only values, I mean basically i want the same object,but with only selected properties.

Mike Hogan Over a year ago

@bhargav,I tidied it up a bit more - the earlier solution was annoying me:)

bhargav Over a year ago

i dont want to use the plucked solution, i want to get the sub properties as separate items,like [{"prop3.name":"tom","prop3.age":"24"},{"prop3.name":"cat","prop3.age":"25"}]

bhargav Over a year ago

currently i am getting like this [{"prop3":{"name":"tom","age":"24"}},{"prop3":{"name":"cat","age":"25"}}]

Mike Hogan Over a year ago

so you want to flatten the structure? you just want a flat array of objects containing the wanted properties?

|

haitaka · Accepted Answer · 2013-03-05 11:36:12Z

2

I don't know about Underscore.js, but you may try this code:

function pick(obj,list){
    var newObj={};
    for(var i=0;i<list.length;i++){
        var str=list[i].split('.');
        var o=obj[str[0]];
        for(var j=1;j<str.length;j++){
            o=o[str[j]];
        }
        newObj[list[i]]=o;
    }
    return newObj;
}

answered Mar 5, 2013 at 11:36

haitaka

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Comments

Community · Accepted Answer · 2020-06-20 09:12:55Z

1

Underscore Deep Pick Plugin

I've created this plugin for underscore.js to help with problems like this.

Deep Pick Pluging

Available at NPM and Bower

npm install deep_pick
bower install deep_pick

Example:

var input = {
  one: 1,
  two: true,
  three: 'Three',
  four: [1,2,3,4],
  five: {
    alpha: 1,
    beta: 2,
    gamma: 3,
    teta: {
        alef: 1,
        beh: 2,
        peh: 3
    }
  },
  answer: '42.00',
  description: 'This is an object.'
};


var schema = {
  one: true,
  three: true,
  five: {
    alpha: true,
    teta: {
      beh: true
    }
  }
};

deepPick(input, schema); // =>

{
  one: 1,
  three: "Three",
  five: {
    alpha: 1,
    teta: { 
      beh: 2
    }
  }
}

edited Jun 20, 2020 at 9:12

CommunityBot

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answered May 23, 2014 at 22:59

Mohsen

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Comments

svestka · Accepted Answer · 2014-02-17 17:52:27Z

I've created a simple gist exactly for this: https://gist.github.com/peterslivka/9055188

_.mixin({ 
    pickDeep: function(obj) {
        var copy = {},
            keys = Array.prototype.concat.apply(Array.prototype, Array.prototype.slice.call(arguments, 1));

        this.each(keys, function(key) {
            var subKeys = key.split('.');
            key = subKeys.shift();

            if (key in obj) {
                // pick nested properties
                if(subKeys.length>0) {
                    // extend property (if defined before)
                    if(copy[key]) {
                        _.extend(copy[key], _.pickDeep(obj[key], subKeys.join('.')));
                    }
                    else {
                        copy[key] = _.pickDeep(obj[key], subKeys.join('.'));
                    }
                }
                else {
                    copy[key] = obj[key];
                }
            }
        });

        return copy;
    }
});

You can find working example here: http://jsfiddle.net/TFfHk/

styks · Accepted Answer · 2016-01-11 20:07:06Z

0

In case someone finds there way here. The _.pluck function is what you want. Comes with underscore.

http://underscorejs.org/#pluck

answered Jan 11, 2016 at 20:07

styks

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Comments

nof · Accepted Answer · 2016-06-24 21:59:40Z

lodash has some great methods for checking for and setting deep object properties: has, set, & get. You can use these functions to build up your own deepPick / deepPluck function. Below is an ES6 style function that builds on lodash and uses the built in Array.reduce method. Just a note that lodash uses the dot delimiter for nested properties.

/**
 * Deep pick / pluck properties.
 *
 * @param {object} the source object
 * @param {array[string]} the properties to pick
 */
function deepPick (source, props) {
  return props.reduce((result, key) => {
    const exists = lodash.has(source, key);

    if (exists) {
      lodash.set(result, key, lodash.get(source, key));
    }

    return result;
  }, {});
}

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