Calculate superficial area and volume of mesh with Three.js(WebGL)

//Created by Ken on Oct 20,2016 for volume compute when upload
function SignedVolumeOfTriangle(p1, p2, p3) {
var v321 = p3.X*p2.Y*p1.Z;
var v231 = p2.X*p3.Y*p1.Z;
var v312 = p3.X*p1.Y*p2.Z;
var v132 = p1.X*p3.Y*p2.Z;
var v213 = p2.X*p1.Y*p3.Z;
var v123 = p1.X*p2.Y*p3.Z;
var singnedVolume=(1/6)*(-v321 + v231 + v312 - v132 - v213 + v123);
return singnedVolume;
}

function VolumeOfMesh(points) {

var i= 0,vols=0;
var P1,P2,P3;
do
{
P1={X:points[i],Y:points[i+1],Z:points[i+2]};
P2={X:points[i+3],Y:points[i+4],Z:points[i+5]};
P3={X:points[i+6],Y:points[i+7],Z:points[i+8]};

vols+=SignedVolumeOfTriangle(P1, P2, P3);
i+=9;
}
while (i<points.length);

return customRound(Math.abs(vols)/1000,2);
}
function customRound(number,fractiondigits){
with(Math){
return round(number*pow(10,fractiondigits))/pow(10,fractiondigits);
}
}

function SuperficialAreaOfMesh(points) {

var _len =points.length,
_area = 0.0;

if (!_len) return 0.0;

var i= 0,vols=0;
var va,vb,vc;
do
{
va={X:points[i],Y:points[i+1],Z:points[i+2]};
vb={X:points[i+3],Y:points[i+4],Z:points[i+5]};
vc={X:points[i+6],Y:points[i+7],Z:points[i+8]};

var ab = {X:vb.X-va.X,Y:vb.Y-va.Y,Z:vb.Z-va.Z};
//vb.clone().sub(va);
var ac = {X:vc.X-va.X,Y:vc.Y-va.Y,Z:va.Z-vc.Z};
//vc.clone().sub(va);

var cross = new THREE.Vector3();
cross=crossVectors( ab, ac );
_area += Math.sqrt(Math.pow(cross.X,2)+Math.pow(cross.Y,2)+Math.pow(cross.Z,2))/2;
i+=9;
}
while (i<points.length);

return customRound(Math.abs(_area)/100,2);

}

function crossVectors( a, b ) {
var ax = a.X, ay = a.Y, az = a.Z;
var bx = b.X, by = b.Y, bz = b.Z;
var P={X:ay * bz - az * by,
Y:az * bx - ax * bz,
Z:ax * by - ay * bx}

return P;
}