Reading file contents on the client-side in javascript in various browsers

Tackling browser diversity

FileReader API is widely supported in modern browsers including Firefox, Chrome, Safari, and Edge. Yet, minor differences arise:

• WebKit browsers, like Safari, once used fileName and fileSize keys, now standardized as name and size in the File API specification.

Always refer to Can I Use for the latest browser compatibility information.

##Non-text files and dinosaurs (aka legacy browsers)

For non-text files, readAsBinaryString or readAsArrayBuffer are your alternatives. However, relics like Internet Explorer may require unique tactics:

• Older IE versions might call for ActiveX object. Scripting.FileSystemObject can read files, but is usually sidestepped due to security concerns.

When FileReader isn't supported, polyfills like blob-polyfill can fill functionality gaps.

Error handling and not playing with fire (security)

Implement compact error handling using try-catch blocks and FileReader's onerror event for error finesse.

reader.onerror = (error) => {
  console.error('Error reading file:', error); // screaming in console, yikes!
};
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Bear in mind the security implications when permitting client-side file reading. Handle file data responsibly to avoid summoning internet trolls!

Advanced File maneuvers

Asynchronous reading for fun and profit with async/await

async/await can streamline file reading operations. Here's a blueprint:

document.querySelector('input[type="file"]').onchange = async (e) => {
  const reader = new FileReader();
  reader.onload = () => console.log(reader.result); // freshly baked content!

  try {
    const file = e.target.files[0];
    await reader.readAsText(file); // async magic unfolds here!
  } catch (error) {
    console.error(error); // error, the uninvited party guest!
  }
};
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After the load party: processing files

Capitalize on the load event to manipulate file content, like hashing or parsing:

reader.onload = () => {
  // Process reader.result after reading 
  const fileContentHash = someHashFunction(reader.result); // cooking the hash!
  console.log(fileContentHash); // serving the dish!
};
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Live telecast in DOM

Display read content in DOM elements with innerText or innerHTML:

reader.onload = () => {
  document.getElementById('file-content').innerText = reader.result; // voila, instant display!
};
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Always sanitize content using innerHTML - better safe than sorry from XSS attacks.

Standards, contributions, and your mark on the internet

The File API thrives in the living HTML5 specification. Join the WHATWG mailing list or suggest changes to contribute to a more standardized API and improved cross-browser compatibility.