Was there an issue with supporting outdated browsers (Internet Explorer, etc.)? How was cross-browser compatibility addressed?

Support issues with outdated browsers like Internet Explorer often arose due to the lack of modern standards and APIs that these browsers did not support. To address cross-browser compatibility, several approaches were used:

• Using polyfills to add support for new JavaScript features and DOM APIs.
• Transpiling code with Babel to convert modern JavaScript into an older version compatible with IE.
• Using CSS prefixes and fallback styles to ensure proper display.
• Testing across different browsers and versions using tools like BrowserStack.
• Limiting the use of new features or providing alternatives.

For example, if the method Array.prototype.includes is used, which is not available in IE, a corresponding polyfill is added or replaced with indexOf:

if (!Array.prototype.includes) {
  Array.prototype.includes = function(searchElement /*, fromIndex*/) {
    return this.indexOf(searchElement) !== -1;
  };
}

Thus, supporting older browsers requires additional work, but with modern tools and approaches, acceptable compatibility can be achieved.