Backend and Frameworks

Table of Content

Compatibility and Performance

Ensuring that JavaScript code runs smoothly across different browsers and optimizing performance are key aspects of web development. This section covers techniques for handling cross-browser compatibility, performance optimization, and best practices for efficient JavaScript execution.

This Privacy Policy describes how Alevio ("we,"

"our," or "us"), founded and led by Felix Danyluk (CEO and Founder), collects, uses, and discloses your information when you use our application, website, and services (collectively, the "Service").

Wichtig: Alevio ist als privacy-first Anwendung konzipiert. Alle deine persönlichen Daten werden lokal auf deinem Gerät gespeichert und nicht an unsere Server übertragen, es sei denn, du aktivierst explizit Cloud-Funktionen.

1. Information We Collect

Alevio operates primarily as a local application.

The information stored includes:

• Personal information: name and preferences (stored locally only).

• Usage data: daily responses and insights (stored locally only).

• Device information: app preferences and settings (stored locally only).

• Al Chat data: when using Al features, messages are sent to OpenAl for processing.

2. How We Use Your Information

We use the information we collect to:

• Provide, maintain, and improve our Service.

• Personalize your experience.

• Communicate with you about our Service.

• Monitor and analyze trends, usage, and activities.

3. Sharing Your Information

We may share your information with:

• Service providers who perform services on our behalf.

• Business partners with whom we jointly offer products or services.

• Law enforcement or other third parties when required by law.

4. Data Security

We implement appropriate technical and organizational measures to protect the security of your personal information. However, please note that no method of transmission over the note that no method of transmission over the Internet or method of electronic storage is 100% secure.

5. Your Choices

You can access, update, or delete your account information at any time by logging into your account settings. You may also contact us directly to request access to, correction of, or deletion of any personal information that you have provided to us.

6. Children's Privacy

Our Service is not intended for children under the age of 13. We do not knowingly collect personal information from children under 13. If you are a parent or guardian and you are aware that your child has provided us with personal information, please contact us.

7. Changes to This Privacy Policy

We may update our Privacy Policy from time to time. We will notify you of any changes by posting the new Privacy Policy on this page.

8. Company Information

Alevio is founded and led by Felix Danyluk, CEO and Founder. Our commitment to privacy and data protection is a core value of our leadership team.

9. Contact Us

If you have any questions about this Privacy Policy, please contact us at privacy.alevio@gmail.com

Handling Cross-Browser Compatibility

Different browsers interpret JavaScript slightly differently. Developers must ensure that their code works consistently across modern browsers like Chrome, Firefox, Safari, Edge, and even older versions of Internet Explorer when necessary.

Feature Detection Using `if` Statements

Before using a feature, check if the browser supports it.

if ("geolocation" in navigator) {
  navigator.geolocation.getCurrentPosition(position => {
    console.log("Latitude:", position.coords.latitude);
  });
} else {
  console.log("Geolocation is not supported in this browser.");
}

Using `try...catch` for Fallbacks

For features that may throw errors in unsupported browsers:

try {
  let speech = new SpeechSynthesisUtterance("Hello");
  window.speechSynthesis.speak(speech);
} catch (error) {
  console.log("Speech API not supported.");
}

Using Polyfills

A polyfill is JavaScript code that provides modern functionality in older browsers.

Example: Adding fetch() support for older browsers:

<script src="https://cdnjs.cloudflare.com/ajax/libs/fetch/3.6.2/fetch.min.js"></script>

Reducing JavaScript Execution Time

Minifying JavaScript removes unnecessary characters to reduce file size.

Use Terser or UglifyJS to minify scripts:

Load scripts asynchronously to prevent blocking the page load.

async: Loads in parallel but executes immediately.

defer: Loads in parallel and executes after HTML parsing is complete.

<script src="script.js" async></script>
<script src="script.js" defer></script>

Reduce Unnecessary DOM Manipulation

Frequent DOM changes can slow down performance.

Inefficient:

for (let i = 0; i < 100; i++) {
  document.body.appendChild(document.createElement("p"));
}

Efficient (using DocumentFragment):

let fragment = document.createDocumentFragment();
for (let i = 0; i < 100; i++) {
  let p = document.createElement("p");
  fragment.appendChild(p);
}
document.body.appendChild(fragment);

Optimizing Loops and Event Listeners

Use Efficient Loops

forEach() and map() are convenient but for loops can be faster for large datasets.

let arr = new Array(100000).fill(0);

console.time("forEach");
arr.forEach(num => num + 1);
console.timeEnd("forEach");

console.time("for-loop");
for (let i = 0; i < arr.length; i++) {
  arr[i] + 1;
}

console.timeEnd("for-loop");

Throttle and Debounce Events

Expensive event listeners (e.g., scroll, resize) can degrade performance.

Debouncing ensures the function runs only after the event has stopped firing.
Throttling ensures the function runs at a fixed interval, even if the event continues firing.

Debounce Example

function debounce(func, delay) {
  let timer;
  return function () {
    clearTimeout(timer);
    timer = setTimeout(() => func.apply(this, arguments), delay);
  };
}
  
window.addEventListener("resize", debounce(() => {
  console.log("Resize event fired!");
}, 300));

Throttle Example

function throttle(func, limit) {
  let lastCall = 0;
  return function () {
    let now = Date.now();
    if (now - lastCall >= limit) {
      lastCall = now;
      func.apply(this, arguments);
    }
  };
}
  
window.addEventListener("scroll", throttle(() => {
  console.log("Scroll event fired!");
}, 200));

Use Web Workers for Heavy Computations

Web Workers allow running JavaScript in the background without blocking the main thread.

Creating a Web Worker

let worker = new Worker("worker.js");

worker.postMessage("Start");
  
worker.onmessage = event => {
  console.log("Worker Response:", event.data);
};

worker.js

self.onmessage = () => {
  let result = 0;
  for (let i = 0; i < 1e9; i++) {
    result += i;
  }
  postMessage(result);
};

Use Efficient Data Structures

Use Maps Instead of Objects for Large Datasets

let obj = {};
let map = new Map();
  
map.set("key1", "value1");
console.log(map.get("key1"));

Use Set for Unique Values

let uniqueNumbers = new Set([1, 2, 3, 3, 4]);
console.log(uniqueNumbers.size); // Outputs: 4

Conclusion

Optimizing JavaScript ensures better browser performance and compatibility. This section covered techniques for reducing execution time, handling memory leaks, improving event handling, and using efficient data structures. The next section will focus on JavaScript in the Backend with Node.js, covering server-side development with JavaScript.