Category: JavaScript Answers

To fix Leaflet Map container not found error with JavaScript, we should make sure we call L.map after the map container element is added.

For instance, we write

<div id="leafletmap"></div>

to add the map container element.

Then we call L.map('leafletmap') to render the map in the div.

To fix JavaScript Date().getTime() is not a function, we need the new keyword before Date.

For instance, we write

const now = new Date().getTime();

to create a new date object with new Date().

And then we call getTime to get the current timestamp from the date object.

To access EJS variable in JavaScript logic, we can inject the variable directly into the EJS template.

For instance, we write

<% if (gameState) { %>
<script>
  let clientGameState = <%= gameState %>
</script>
<% } %>

to get the gameState variable with <%= gameState %> and assign that to the clientGameState variable in the script tag.

To add multiple classes with function with d3 and JavaScript, we use the attr method.

For instance, we write

d3.selectAll(".user").attr("data-name", (d, i) => {
  return `Michael #${i}`;
});

to select all elements with class user with selectAll.

And then we call attr with the attribute name we want to set for each selected element.

The callback returns the value of the data-name attribute. And i is the index of the element being iterated through to set the attribute.

To run HTML file using Node.js, we call readFile to read the file and http module.

For instance, we write

const http = require("http");
const fs = require("fs");

const PORT = 8080;

fs.readFile("./index.html", (err, html) => {
  if (err) throw err;

  http
    .createServer((request, response) => {
      response.writeHeader(200, { "Content-Type": "text/html" });
      response.write(html);
      response.end();
    })
    .listen(PORT);
});

to call readFile to read index.html.

And then we serv it by call http.createServer to start a web server with a callback that calls write with the html file content to serve that.