When you can't access the console, this script will display errors and warnings over the html (ensure this runs before your own code)

show-errors.js

(() => {
	let errorDisplayEl = document.createElement('div');
	errorDisplayEl.classList.add('error-display');
	errorDisplayEl.style.display = 'none';
	errorDisplayEl.style.position = 'absolute';
	errorDisplayEl.style.zIndex = '2000';
	errorDisplayEl.style.backgroundColor = 'rgba(146, 0, 0, 0.6)';
	errorDisplayEl.style.padding = '20px';
	errorDisplayEl.style.fontFamily = 'monospace, sans-serif';
	errorDisplayEl.style.color = '#fff5f5';
	errorDisplayEl.style.backdropFilter = 'blur(10px)';
	errorDisplayEl.style.width = '100%';
	errorDisplayEl.style.overflow = 'scroll';
	document.body.prepend(errorDisplayEl);

	let closeButtonEl = document.createElement('button');
	closeButtonEl.classList.add('close-button');
	closeButtonEl.innerHTML = '×';
	closeButtonEl.style.color = 'white';

	closeButtonEl.style.position = 'absolute';
	closeButtonEl.style.right = '5px';
	closeButtonEl.style.top = '5px';
	closeButtonEl.style.border = 'none';
	closeButtonEl.style.width = '30px';
	closeButtonEl.style.height = '30px';
	closeButtonEl.style.fontSize = '30px';
	closeButtonEl.style.lineHeight = '30px';
	closeButtonEl.style.padding = '0';
	closeButtonEl.style.fontWeight = '100';
	closeButtonEl.style.background = 'none';
	closeButtonEl.style.cursor = 'pointer';
	closeButtonEl.style.webkitTouchCallout = 'none';
	closeButtonEl.style.webkitUserSelect = 'none';
	closeButtonEl.style.khtmlUserSelect = 'none';
	closeButtonEl.style.mozUserSelect = 'none';
	closeButtonEl.style.msUserSelect = 'none';
	closeButtonEl.style.userSelect = 'none';

	errorDisplayEl.appendChild(closeButtonEl);

	let errorContentEl = document.createElement('div');
	errorContentEl.classList.add('error-content');
	errorDisplayEl.appendChild(errorContentEl);

	closeButtonEl.addEventListener('click', () => {
		errorDisplayEl.style.display = 'none';
		// clear content
		errorContentEl.innerHTML = '';
	});

	function showError(message) {
		errorDisplayEl.style.display = 'block';
		let errorEl = document.createElement('p');
		errorEl.innerHTML = message;
		errorContentEl.appendChild(errorEl);
	}

	// override console.error
	let _console_error = window.console.error;
	let _console_warn = window.console.warn;
	window.console.error = function() {
		let args = Array.prototype.slice.call(arguments);
		showError('<b>Console.error:</b> ' + args.join(', '));
		_console_error.apply(this, args);
	}
	window.console.warn = function() {
		let args = Array.prototype.slice.call(arguments);
		showError('<b>Console.warn:</b> ' + args.join(', '));
		_console_warn.apply(this, args);
	}

})();