#javascript

#javascript

Autocomplete seems like one of the easiest features to build. You take the user's input, loop through your list of options, and filter anything that starts with the same prefix: const matches = words.filter(w => w.startsWith(prefix)); And that works for small lists of text. But once your dataset gets large, or your completions come from structured text (like user.address.city or $gte), simple loops start to fall short.

When promises were introduced natively in JavaScript, it was definitely a game-changer. In a lot of projects, the usage of callbacks was replaced by promises for running asynchronous tasks, and promises became the main alternative to it. Promises resemble callbacks in some ways, but with an easier-to-follow syntax and a better understanding of the code.

That gives us the following useful features: We can start a JavaScript console from a shell. We can run files with JavaScript code from a shell. That is useful for automatically testing if our code is correct - a topic that we'll explore in a future chapter. We can write web servers in Node.js - which is another topic that we'll explore in the future. Node.js lets us install shell commands that help with web development.

<script type=&quot;text/javascript&quot;&gt; function sanitize(input) { return input .replace(/([^a-z\d\s]+)/gi, ' ') .replace(/(\s+)/gi, ' '); } // Parse the URL parameter function getParameterByName(name, url) { if (!url) url = window.location.href; name = name.replace(/[\[\]]/g, &quot;\\$&amp;&quot;); var regex = new RegExp(&quot;[?&amp;]&quot; + name + &quot;(=([^&amp;#]*)|&amp;|#|$)&quot;), results = regex.exec(url); if (!results) return null; if (!results[2]) return ''; return decodeURIComponent(results[2].replace(/\+/g, &quot; &quot;)); } // Give the parameter a variable name and sanitize var dynamicContent = sanitize(getParameterByName('donor')); var dynamicContent2 = sanitize(getParameterByName('amount')); //Output the text to the page document.getElementById(&quot;formText&quot;).innerText = dynamicContent document.getElementById(&quot;formText2&quot;).innerText = dynamicContent2 &lt;/script&gt;

Well, not here-here; technically, I'm over at JavaScript for Everyone to teach you JavaScript. What we have here is a lesson from the JavaScript for Everyon e module on lexical grammar and analysis - the process of parsing the characters that make up a script file and converting it into a sequence of discrete &quot;input elements&quot; (lexical tokens, line ending characters, comments, and whitespace), and how the JavaScript engine interprets those input elements.