Example: error in console says “Find me!”
Example: error in console says “Find me!”
JavaScript error in console says “Find me!”

We do not know if our web application works 100% on different devices unless we observe them. I see a benefit of QuickSight to enable visualization of issues when many users face JavaScript errors and developers want to understand the issues in detail. Amplify seems to be a good starting point to enter AWS for JavaScript developers and I introduce how to quickly integrate observability into front-end development with the two services.


Observability in product development is to detect where and when bad user experience happens, and get an idea of what causes that helps the developer reduce time to…

Cannot support custom domain of Cognito hosted UI with Amplify

My app redirected to default URL of Cognito hosted UI when I specified custom domain in Cognito, deactivated default URL of Cognito hosted UI and call Auth.federatedSignIn() in my react app with Amplify.

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Redirected to the default URL of the Cognito hosted UI

The bare minimum code to reproduce is below:

import awsconfig from "./aws-exports";Amplify.configure(awsconfig);Auth.federatedSignIn();

Which is a known issue

Apparently, this is a known issue that Amplify does not support custom domain for Cognito hosted UI yet.

Amplify seems to directly takeconfig.oauth.domain from aws-exports.js

Faced an issue to support multiple redirect URLs for Auth with Amplify

I faced the below issue when I specified multiple redirect URLs and used .federatedSignInwith Amplify module in React app.

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Redirect URL error

The bare minimum code base to reproduce is here:

import awsconfig from "./aws-exports";Amplify.configure(awsconfig);Auth.federatedSignIn();

Which is known issue

This is known issue and basically you need to specify a single URL to your awsconfig before calling Amplify.configure as it’s recommended in the thread.

Some comments in the issue says that you need to copy the Object of the awsconfig, but property of Object in JavaScript is reference as long as you do not do deep copy so that I directly overwrote the props and…

GraphQL server usage in Japan

As same as GraphQL community has been growing, The number of searches in Japan has been also increasing. I started using it a couple years ago and immediately felt a free from manual syncing work between backend APIs and frontend calls. But turned out not many web developers surrounding me in Japan use it and that led me to research how many developers actually used it.

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Source: https://trends.google.com/trends/explore?date=all&geo=JP&q=GraphQL

Quick survey

I asked my follower “GraphQL server usage” by a quick survey in Japanese for 24h and received 232 inputs.

Visualizing in the below:

I was looking for a way for my friend who had never tried programming to run a static server in her local as part of building a development environment without using a terminal.

Then I built a GUI app -

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Code first and fun

What experience can be the best to start programming? The key would be an interaction. Coding and seeing the result makes beginners fun. I see many beginners get frasttated when takes time to build development environment and give up right after.

Code GUI app with JavaScript

Tten building a simple app that they want to use will be the second step of the journey. Once they reach this step, they start enjoying their learning mostly.

Hope my solution will make more hackers. Happy hacking!

At the end of last year, I was looking for systematic learning materials to help people learn web technology through experiential learning, and Google recommended its “Mobile Web Specialist” certification.

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In January, I took the exam without giving it much thought and failed, even though I code JavaScript on a daily basis. By taking the examination, I was able to determine my weak areas, and I set aside some time in March to improve upon them. Then I took the exam again in April and passed.

My conclusion is that it was a very good experience.

I was casting a sideways glance at the recent popularity of TypeScript aside and thinking that I would become the last person who continues writing JavaScript until today.

I was writing a simple function with async/await like the below.

function delay(msec, count) {
return new Promise<number>(resolve => {
setTimeout(() => {
}, msec);
async function dramatic() {
for (let i = 0; i < 5; i++) {
const count = delay(500, i);

You would realise that this code will make an error in the dramatic function. delay(500, i); should be awaited, but I…

I am neither a ramen maker nor a Dr. Ramen. I’m just a person who has eaten more ramen than average since I grew up in Tokyo, Japan.

Several years have passed since I moved to Europe, I’ve visited nine countries so far and I usually go ramen when I visit a city for the first time. What I was feeling is mostly these ramen restaurants in Europe are focusing on Tonkotsu taste as their main ramen. Fair enough, because it’s same with Tokyo. Tonkotsu would be the most popular ramen taste in the world. …

I was watching a Japanese TV show called “Eigo de Shabera Night”. It’s a talk show and the main topic is about English. At the show, a professional simultaneous interpreter was participating as a guest. It was a very interesting topic that she spoke about the pain of the simultaneous interpreter. I will note it here.

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Translating jokes

Shinoda Akiko is a simultaneous interpreter specializing in politics and the environment. She interpreted the inauguration of presidents Clinton and Mandela. 26 years of simultaneous interpreting, she’s communicated many historic moments.

MC: I imagine one of the hardest areas for you to translate. …

This is a question I worked on in some process before. I felt that it wasteful to throw away, so I will keep it as a note in Medium.

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Go to https://github.com/settings/profile, choose one of the settings screens on the left as your focus. What’s the one thing you would change about it? Explain your reasoning and how you would change it.


Currently, if a developer is an owner of many popular repositories, potentially they’re receiving hundreds of emails every day. Those kinds of developers may have a filter in their email client, but if not, they would easily get…

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