# javascript - multiply the result of subtracting one value from another

I would like to multiply:

``vectorDiff = placementPosition.sub(viewerPosition);``

by 10, so that when "model" is moved:

``moveModel(vectorDiff, "GPS");``

it moves 10 times more than it is currently. How do i do this; im new to javascript any help would be greatly appreciated. The following is the code block the above is located in:

``if ( viewerPosition !== null && placementPosition!== null) {vectorDiff = placementPosition.sub(viewerPosition);rotationSum = new THREE.Vector3().addVectors(placementRotation, viewerRotation)//rotationSum.setY(rotationSum.y+180);moveModel(vectorDiff, "GPS");//rotateModel(rotationSum, "GPS");``

Three.js vectors are mutable; when you call `v1.sub(v2)`, `v1` contains the result:

``````var v1 = new THREE.Vector3(2,3,4);
var v2 = new THREE.Vector3(1,0,3);

v1.sub(v2);
console.log(v1.toArray())
// [1, 3, 1]
``````

Therefore "the result of subtracting one value from another" is just "the first vector". You need a way to multiply that vector by a single number, or scalar.

That method is `multiplyScalar`:

``````v1.multiplyScalar(10);
console.log(v1.toArray());
// [4, 12, 4]
``````

JSBin

Three.js docs for Vector3