edx-platform/lms/static/js/learner_analytics_dashboard/DueDates.jsx

import React from 'react';
import classNames from 'classnames';
import PropTypes from 'prop-types';

const days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat'];
const months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];

class DueDates extends React.Component {
    constructor(props) {
        super(props);
    }

    getDate(str) {
        const date = new Date(str);
        const day = days[date.getDay()];
        const month = months[date.getMonth()];
        const number = date.getDate();
        const year = date.getFullYear();

        return `${day} ${month} ${number}, ${year}`;
    }

    getLabel(type) {
        const {assignmentCounts} = this.props;
        if (assignmentCounts[type] < 2) {
            return type;
        } else {
            this.renderLabels[type] += 1;
            return type + ' ' + this.renderLabels[type];
        }
    }

    getList() {
        const {dates, assignmentCounts} = this.props;
        this.renderLabels = this.initLabelTracker(assignmentCounts);

        return dates.sort((a, b) => new Date(a.due) > new Date(b.due))
            .map(({format, due}, index) => (
                <li className="date-item" key={index}>
                    <div className="label">{this.getLabel(format)}</div>
                    <div className="data">{this.getDate(due)}</div>
                </li>
            ));
    }

    initLabelTracker(list) {
        let labels = Object.keys(list);

        return labels.reduce((accumulator, key) => {
            accumulator[key] = 0;
            return accumulator;
        }, {});
    }

    renderList() {
        return (
            <ul className="date-list">
                {this.getList()}
            </ul>
        );
    }

    render() {
        return (
            <div className="due-dates">
                {this.renderList()}
            </div>
        );
    }
}

DueDates.propTypes = {
    dates: PropTypes.array.isRequired
};

export default DueDates;