I ended up adding a bind to the end( I'm very bad at javascript it turns out... )
tween.onUpdate(function( tween ){
if( this.type == 'position' ){ this.object.position.x = this.initial.x; this.object.position.y = this.initial.y; this.object.position.z = this.initial.z; }else if( this.type == 'scale' ){ this.object.scale.x = this.initial.x; this.object.scale.y = this.initial.y; this.object.scale.z = this.initial.z; }
if( this.initial.x == this.target.x ){
var i = this.tweener.tweens.indexOf( this );
this.tweener.tweens.splice( i , 1 );
this.callback();
}
}.bind( tween ));