Author: John Au-Yeung

To upload base64 encoded Image to Amazon S3 via Node.js, we call the putObject method.

For instance, we write

const AWS = require("aws-sdk");
AWS.config.loadFromPath("./s3_config.json");
const s3Bucket = new AWS.S3({ params: { Bucket: "myBucket" } });
const buf = Buffer.from(
  req.body.imageBinary.replace(/^data:image\/\w+;base64,/, ""),
  "base64"
);
const data = {
  Key: req.body.userId,
  Body: buf,
  ContentEncoding: "base64",
  ContentType: "image/jpeg",
};
s3Bucket.putObject(data, (err, data) => {
  if (err) {
    console.log(err);
    console.log("Error uploading data: ", data);
  } else {
    console.log("successfully uploaded the image!");
  }
});

to convert the base64 string to a buffer with the Buffer.from method.

We replace the prefix with 'base64' before doing the conversion with replace.

Then we create a data object with Body set to the buf buffer.

Finally, we call putObject to upload the data.

To change working directory in my current shell context when running Node.js script, we call the process.chdir method.

For instance, we write

const process = require("process");
process.chdir("../");

to call the process.chdir method to go up one directory level.

To pass arguments to require (when loading module) with Node.js, we export a function.

For instance, we write

class MyClass {
  constructor(arg1, arg2, arg3) {}
  myFunction1() {}
  myFunction2() {}
  myFunction3() {}
}

module.exports = (arg1, arg2, arg3) => {
  return new MyClass(arg1, arg2, arg3);
}

in myClass.js to export a function that returns the MyClass instance.

Then we write

const MyClass = require("/myClass.js")(arg1, arg2, arg3);

in app.js to import myClass.js and call its constructor with the arguments.

To fix npm ERR! Refusing to delete / code EEXIST error with JavaScript, we delete the node_modules and reinstall all the packages.

After deleting the node_modules folder, we reinstall all the packages with

npm install

To connect to TCP Socket from browser using JavaScript, we call the socket.create method.

For instance, we write

chrome.experimental.socket.create("tcp", "127.0.0.1", 8080, (socketInfo) => {
  chrome.experimental.socket.connect(socketInfo.socketId, (result) => {
    chrome.experimental.socket.write(socketInfo.socketId, "Hello, world!");
  });
});

to call the socket.create method to create a socket to 127.0.0.1 port 8080.

We then call socket.connect method to connect to the socket with the socketInfo.

And then we call write to send data to the socket.