converting results from SQL tables (split into multiple arrays) into an object in js [duplicate]

I get results from a query where each field is a separate table. For exemple, for this table (ordered by Product, Step) :

PRODUCT | STEP      | WORKER
Car     | Polishing | Carl
Car     | Painting  | Peter
Car     | Painting  | Mark
Bike    | Painting  | Paul
Boat    | Repairing | Alex

I'll have 3 tables (Product, Step, Worker). I'd need to put this in another object ending up like that :

var factory = [
    [
        [{"product":"Car","step":"polishing","workers":[{"name":"Carl"}]}],
        [{"product":"Car","step":"painting","workers":[{"name":"Peter"},{"name":"Mark"}]}]
    ],
    [
        [{"product":"Bike","step":"painting","workers":[{"name":"Paul"}]}]
    ],
    [
        [{"product":"Boat","step":"repairing","workers":[{"name":"Alex"}]}]
    ]
]

I'm using javascript. Could anyone help please ?

Here's what I tried :

var factory = [];
var currentProduct = [];
var currentStep = [];
var currentWorker = {"name":workers[0]};
var currentStepItem = {
    "product":product[0],
    "step":step[0],
    "workers":[currentWorker]
};
currentStep.push(currentStepItem);
currentProduct.push(currentStep);
factory.push(currentProduct);

for(var i = 1 ; i < product.length ; i++){
    if(product[i] == product[i-1]){
        //I'm stuck here
    }
}