three.js/examples/jsm/WebGL.js

var WEBGL = {

	isWebGLAvailable: function () {

		try {

			var canvas = document.createElement( 'canvas' );
			return !! ( window.WebGLRenderingContext && ( canvas.getContext( 'webgl' ) || canvas.getContext( 'experimental-webgl' ) ) );

		} catch ( e ) {

			return false;

		}

	},

	isWebGL2Available: function () {

		try {

			var canvas = document.createElement( 'canvas' );
			return !! ( window.WebGL2RenderingContext && canvas.getContext( 'webgl2' ) );

		} catch ( e ) {

			return false;

		}

	},

	getWebGLErrorMessage: function () {

		return this.getErrorMessage( 1 );

	},

	getWebGL2ErrorMessage: function () {

		return this.getErrorMessage( 2 );

	},

	getErrorMessage: function ( version ) {

		var names = {
			1: 'WebGL',
			2: 'WebGL 2'
		};

		var contexts = {
			1: window.WebGLRenderingContext,
			2: window.WebGL2RenderingContext
		};

		var message = 'Your $0 does not seem to support <a href="http://khronos.org/webgl/wiki/Getting_a_WebGL_Implementation" style="color:#000">$1</a>';

		var element = document.createElement( 'div' );
		element.id = 'webglmessage';
		element.style.fontFamily = 'monospace';
		element.style.fontSize = '13px';
		element.style.fontWeight = 'normal';
		element.style.textAlign = 'center';
		element.style.background = '#fff';
		element.style.color = '#000';
		element.style.padding = '1.5em';
		element.style.width = '400px';
		element.style.margin = '5em auto 0';

		if ( contexts[ version ] ) {

			message = message.replace( '$0', 'graphics card' );

		} else {

			message = message.replace( '$0', 'browser' );

		}

		message = message.replace( '$1', names[ version ] );

		element.innerHTML = message;

		return element;

	}

};

export { WEBGL };