How to put an if statement inside a for loop?

I want to change the alue of "volgendecylinder" when I am at the last number of the loop.

I tried this but this doesnt seem to work.

for (i = 1; i < aantalDwars; i++)
    { 

    var geometry2 = new THREE.CylinderGeometry( dwarsDiameter * scale , dwarsDiameter * scale , lengte2*scale , 20 );
    var material2 = new THREE.MeshBasicMaterial( {color: 0xe4734f} );
    var cylinder2 = new THREE.Mesh( geometry2, material2 );
    cylinder2.userData.type = 'cylinder';

    scene.add( cylinder2 );
if (i = aantalDwars){
    volgendeCylinder = ((lengte*scale)/2) + uitsteekLinks

    }

    cylinder2.position.set( ((lengte*scale)/2)+volgendeCylinder2, 1 , 0);
    volgendeCylinder2 -= (dwarsMaas*scale);
    cylinder2.rotation.x = Math.PI / 2;


}