Transform array of objects with Underscore

Question

I'm trying to take an array of objects and pick out the data that I only need. For example, below I only want the name, id, and users properties from the originalArray.

I figured out how to do it at the first level of iteration, but how do I do the same for the users array of objects? I only want to include the values in the allowedUserProps array found below.

https://jsfiddle.net/n8zw47cd/

Original Array

var originalArr = [
    {
      name: 'Obj 1',
      id: 0,
      something: 'else',
      users: [{first_name: 'Joe', last_name: 'Smith'}]
    }, 
    {
      name: 'Obj 2',
      id: 1,
      something: 'else',
      users: [{first_name: 'Jane', last_name: 'Doe'}]
    }, 
];

Desired Output

[
    {
      name: 'Obj 1',
      id: 0,
      users: [{first_name: 'Joe'}]
    }, 
    {
      name: 'Obj 2',
      id: 1,
      users: [{first_name: 'Jane'}]
    }, 
];

I'm using Underscore's pick method to return whitelisted values, but how can I change the users array of objects too?

function changeArray(arr) {
    var allowedProps = ['name', 'id', 'users'];
    var allowedUserProps = ['first_name'];

    return _.map(arr, function(item) {
       return _.pick(item, allowedProps);
    });
}

var transformed = changeArray(originalArr);

TimoStaudinger · Accepted Answer · 2016-02-02 05:12:00Z

3

Apply another map/pick to the sub-array:

function changeArray(arr) {
    var allowedProps = ['name', 'id', 'users'];
    var allowedUserProps = ['first_name'];

    return _.map(arr, function(item) {
        var out = _.pick(item, allowedProps);
        out.users = _.map(out.users, function(usersItem) {
            return _.pick(usersItem, allowedUserProps);
        });
        return out;
    });
}

Same principle as for the outer array, but once for each sub-array element. This will give you the desired output.

answered Feb 2, 2016 at 5:12

TimoStaudinger

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