JSFiddle - React, Tailwind, and code Playground

HTML

<script src="//cdn.rawgit.com/mrdoob/three.js/master/build/three.min.js"></script>
<script src="//cdn.rawgit.com/mrdoob/three.js/master/examples/js/MarchingCubes.js"></script>

JavaScript

quadValue = function (data, x, y, z) {
	return data.a11*x*x+
		data.a22*y*y+
		data.a33*z*z+
		data.a12*2*x*y+
		data.a13*2*x*z+
		data.a23*2*y*z+
		data.a1*x+
		data.a2*y+
		data.a3*z+
		data.a;
}

quadricData = {
	a11: 3,
	a22: 1,
	a33: 1,
	a12: 0,
	a13: 0,
	a23: 0,
	a1: 0,
	a2: 0,
	a3: 0,
	a: -1
};


var res = 50;
var quadric = new THREE.MarchingCubes( res );

for ( var k = 0 ; k < res ; k++ ) {
	for ( var j = 0 ; j < res ; j++ ) {
		for ( var i = 0 ; i < res ; i++ ) {

			var x = 8*(i-res/2)/res;
			var y = 8*(j-res/2)/res;
			var z = 8*(k-res/2)/res;

			quadric.field[ i + j*res + k*res*res ] = quadValue(quadricData,x,y,z);

		}
	}
}

console.log( JSON.stringify(quadric.field) )