Author: John Au-Yeung

To ping from a Node.js app, we call exec.

For instance, we write

const sys = require("sys");
const exec = require("child_process").exec;

exec("ping -c 3 localhost", (error, stdout, stderr) => {
  sys.puts(stdout);
});

to call exec to run the ping command.

And then we get the output from stdout in the callback.

To make synchronous database queries with Node.js, we use the synchronize module.

For instance, we write

const express = require("express");
const bodyParser = require("body-parser");
const mysql = require("mysql");
const sync = require("synchronize");

const db = mysql.createConnection({
  host: "localhost",
  user: "user",
  password: "password",
  database: "database",
});

db.connect((err) => {
  if (err) {
    console.error("error connecting: " + err.stack);
    return;
  }

  const save = async () => {
    const post = { id: newId };
    const query = sync.await(
      db.query("INSERT INTO mainTable SET ?", post, sync.defer())
    );
    const newId = query.insertId;
    const post = { foreignKey: newId };
    db.query("INSERT INTO subTable SET ?", post, (err, result) => {
      if (err) {
        throw err;
      }
    });
  };
});

to define the save function.

In it, we call sync.await to wait for the query to finish before we move to the next line of code.

We have the save function in the connect callback so we only make queries when the connection is established.

To add basic Ajax send/receive with Node.js, we can use Express and fetch.

For instance, we write

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

app.get("/string", (req, res) => {
  const strings = ["foo", "bar", "baz"];
  const n = Math.floor(Math.random() * strings.length);
  res.send(strings[n]);
});
app.listen(8001);

to add the get /string route which returns a random string from the strings array as the response body with res.send.

Then we write

const res = await fetch("/string");
const string = await res.text();

to make a get request to /string with fetch.

And get the response body with res.text.

To fix Cordova Unable to load platformapi with JavaScript, we remove the platforms.

To do this, we run

ionic cordova platform rm browser/android/ios

to remove the platforms with platform rm.

Then we run

ionic cordova run --emulator

to run the emulator.

To fix TypeError: Request path contains unescaped characters error with Node, we call the encodeURI function.

For instance, we write

const uri = "my test.asp?name=ståle&car=saab";
const res = encodeURI(uri);

to call encodeURI to return an escaped version of the uri string.