Category: JavaScript

To get the width and height of an image in Node.js, we use the image-size package.

For instance, we write

const sizeOf = require("image-size");

sizeOf("images/funny-cats.png", (err, dimensions) => {
  console.log(dimensions.width, dimensions.height);
});

to call the sizeOf function to read the images/funny-cats.png image.

And we get the width and height from the dimensions parameter in the callback.

To fix Date.now().toISOString() throwing error "not a function" with JavaScript, we call toISOString on a date object.

For instance, we write

const now = new Date();
const isoString = now.toISOString();

to create a new Date object now.

Then we call now.toISOString to return the datetime string from the date.

To convert a directory structure in the filesystem to JSON with Node.js, we use the directory-tree package.

To install it, we run

npm i directory-tree

Then we use it by writing

const directoryTree = require("directory-tree");

const tree = directoryTree("/some/path");
const filteredTree = directoryTree("/some/path", [".jpg", ".png"]);

to call directoryTree to return an object of the directory structure with the /some/path folder as root.

We can also call it with a 2nd argument to filter the items by extension.

To run a Node express server using webpack-dev-server, we run the webpack-dev-server command.

For instance, we write

const express = require("express");
const app = express();

require("./_routes")(app);
app.set("port", 8080);
app.listen(app.get("port"), () => {
  console.log("Node App Started");
});

to add an Express app in dev-server.js

Then in package.json, we write

{
  "scripts": {
    "start": "webpack --progress --colors",
    "dev-server": "node dev-server.js",
    "dev-client": "webpack-dev-server --port 3000"
  }
}

to add the dev-client script to run "webpack-dev-server in the dev-client script on port 3000.

To create Node.js server that accepts POST requests, we use the http module.

For instance, we write

const http = require("http");
const server = http.createServer((request, response) => {
  response.writeHead(200, { "Content-Type": "textplain" });
  if (request.method === "GET") {
    response.end("received GET request.");
  } else if (request.method === "POST") {
    response.end("received POST request.");
  } else {
    response.end("Undefined request .");
  }
});

server.listen(8000);

to call createServer with a callback that checks the request method with the request.method property.

If it’s 'POST', then a post request is received.