JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdnjs.cloudflare.com/ajax/libs/underscore.js/1.6.0/underscore-min.js"></script>
<script src="https://code.jquery.com/jquery-2.1.3.min.js"></script>
<div>
     <h3>Data:</h3>

    <div>var data = [
        <br />{ id: 1, name: 'Jon Doe', birthdate: '1/1/1991', height: '5 11'},
        <br />{ id: 2, name: 'Jane Smith', birthdate: '1/1/1981', height: '5 6'},
        <br />{ id: 3, name: 'Rockin Joe', birthdate: '4/4/1994', height: '6 1'},
        <br />{ id: 4, name: 'Jane Blane', birthdate: '1/1/1971', height: '5 9'},
        <br />];</div>
</div>
<div>
     <h3>Transformed:</h3>

    <div class="transformed">result</div>
</div>

JavaScript

var data = [{
    id: 1,
    name: 'Jon Doe',
    birthdate: '1/1/1991',
    height: '5 11'
}, {
    id: 2,
    name: 'Jane Smith',
    birthdate: '1/1/1981',
    height: '5 6'
}, {
    id: 3,
    name: 'Rockin Joe',
    birthdate: '4/4/1994',
    height: '6 1'
}, {
    id: 4,
    name: 'Jane Blane',
    birthdate: '1/1/1971',
    height: '5 9'
}, ];

var transformed = _.indexBy(data, 'id');
$('.transformed').text(JSON.stringify(transformed));