This course picks up where Harvard College’s CS50 leaves off, transitioning from web development to mobile app development with React Native, a popular open-source framework maintained by Facebook that enables cross-platform native apps using JavaScript without Java or Swift. The course introduces students to modern JavaScript (including ES6 and ES7) as well as to JSX, a JavaScript extension. Through hands-on projects, students gain experience with React and its paradigms, app architecture, and user interfaces. The course culminates in a final project for which students implement an app entirely of their own design.


CSCI E-50, CS50x, or equivalent as well as a strong background with HTML and CSS and comfort with basic JavaScript.



Jordan Hayashi

David J. Malan

Teaching Fellow

Yowon Yoon
Software Developer, Raizlabs


You are expected to


Your final grade will be based on your performance on the course’s projects, each of which will bear equal weight. Projects are evaluated primarily along axes of correctness, design, and style, with scores ordinarily determined by 3 × correctness + 2 × design + 1 × style. Scores are normalized across teaching fellows at term’s end. Remarkable effort and upward trending are considered, as is input from the teaching fellows.


Does the project do what it’s supposed to do?

Correctness is determined by the project’s functionality. If the project fulfills the requirements of the project and is otherwise bug-free, you will receive a perfect score on correctness.


Is the project well-architected and/or efficient?

Design score is determined by how well-thought-out the project is. We look at things like balancing efficiency and readability, good abstractions, reuse of common code, etc.


Is the code easy to read?

Style score is determined by code readability and consistency (e.g. consistent indentation/spacing, good variable/function names, etc.).



Lecture 0, 1/22
Overview, JavaScript
Lecture 1, 1/29
JavaScript, ES6
Lecture 2, 2/5
React, Props, State
Lecture 3, 2/12
React Native
Lecture 4, 2/26
Lists, User Input
Lecture 5, 3/5
User Input, Debugging
Lecture 6, 3/19
Guest Lecture on Navigation by Brent Vatne and Eric Vicenti, co-authors of React Navigation
Lecture 7, 3/26
Lecture 8, 4/2
Guest Lecture on Expo Components by Charlie Cheever, founder of Expo
Lecture 9, 4/9
Lecture 10, 4/16
Async Redux, Tools
Lecture 11, 4/23
Lecture 12, 4/30
Deploying, Testing


App Party

From 5:30pm until 7pm on 5/11 will be an end-of-term app party, an opportunity to demo your final project to classmates, staff, and students from other CS50-produced courses. Students are encouraged but not required to travel to campus for the eve. Family and friends are welcome to join.

Academic Honesty

This course’s philosophy on academic honesty is best stated as “be reasonable.” The course recognizes that interactions with classmates and others can facilitate mastery of the course’s material. However, there remains a line between enlisting the help of another and submitting the work of another. This policy characterizes both sides of that line.

The essence of all work that you submit to this course must be your own. Collaboration on assigned projects is not permitted except to the extent that you may ask classmates and others for help so long as that help does not reduce to another doing your work for you. Generally speaking, when asking for help, you may show your code to others, but you may not view theirs, so long as you and they respect this policy’s other constraints. Collaboration on the course’s final project is permitted to the extent prescribed by its specification.

Below are rules of thumb that (inexhaustively) characterize acts that the course considers reasonable and not reasonable. If in doubt as to whether some act is reasonable, do not commit it until you solicit and receive approval in writing from the course’s heads. Acts considered not reasonable by the course are handled harshly. If the course refers some matter for disciplinary action and the outcome is punitive, the course reserves the right to impose local sanctions on top of that outcome that may include an unsatisfactory or failing grade for work submitted or for the course itself. The course ordinarily recommends exclusion (i.e., required withdrawal) from the course itself.

If you commit some act that is not reasonable but bring it to the attention of the course’s heads within 72 hours, the course may impose local sanctions that may include an unsatisfactory or failing grade for work submitted, but the course will not refer the matter for further disciplinary action except in cases of repeated acts.


Not Reasonable

Acknowledgement and Authorization

Harvard plans to record audio, photos, and video of this course’s lectures, labs, sections, office hours, and other events and activities related to the course (the “Recordings”), with the aims of making the content of the course more widely available and contributing to public understanding of innovative learning (the “Projects”). The Recordings, or edited versions of them, may be made available to other Harvard students, to students at other educational institutions, and to the broader public via edX, the Internet, television, theatrical distribution, digital media, or other means. It is also possible that the Recordings may be used to make other derivative works in the future. Students may elect not to appear in photos and video used in the Projects and may still participate fully in the course.

When you submit the course’s first project, you will need to sign online an Acknowledgement and Authorization in the following form:

I understand that, if I do not wish any photos or video of me to be used as part of the Projects, I should so inform the course’s instructor by emailing within one week of enrolling in the course. In that event, I understand that I should sit in the designated “no-film” zone of the course’s classrooms and should not walk in the field of view of the cameras. I understand that Harvard will take reasonable steps, with my cooperation, to avoid including identifiable images of me in the Projects’ photos and video shot in classrooms and other course locations after I opt out as just described. I understand that I am free to opt out of the Projects’ photos and video in this way, and that doing so will not affect my grade or my ability to participate in course activities.

Unless I opt out of the Projects’ photos and video as described above and take the steps that will be outlined by the instructor to avoid being filmed, I authorize Harvard and its designees to record and use photos and video of my participation in the course and activities related to the course (the “Recordings”). I understand and agree that the Recordings may include my image, name, and voice. I also understand and agree that, even if I opt out of the Projects’ photos and video, my spoken name and voice may be picked up by microphones outside the “no-film” zone and may be included in the Recordings.

I understand and agree that Harvard and its designees will have the irrevocable, worldwide right to make, edit, modify, copy, publish, transmit, distribute, sell, publicly display, publicly perform, and otherwise use and make available its respective Recordings and any other works that may be derived from those Recordings, in any manner or medium now known or later invented, and to authorize others to do so as well. I hereby transfer to Harvard any rights, including copyrights, I may have in the Recordings that Harvard makes. I will remain free to use and disseminate any ideas, remarks, or other material that I may contribute to course discussions.

I acknowledge and agree that I will not be entitled to any payment, now or in the future, in connection with the Recordings or any works derived from them. This Acknowledgment and Authorization is a binding agreement, and is signed as a document under seal governed by the laws of the Commonwealth of Massachusetts.

Unless you opt out as described in the Acknowledgment and Authorization, you are agreeing, by attending the course, that your participation in the course and related activities may be recorded and used by Harvard in connection with the Projects without further obligation or liability to you, even if you do not sign any authorization.

If you have any questions about the above, contact