Hi,

In the Odoo 16 Point of Sale module, you can pass an object to specify options such as price, discount, and quantity when adding a product to the order. This eliminates the need for calling the set_quantity() function separately. Here's an example code snippet:

const productId = 293;
var order = this.env.pos.get_order();
var product = this.env.pos.db.get_product_by_id(product_id);
var options = {
   discount: 0,
   merge: false,
   price: -300,
   quantity: 1,
   tax_ids: []
};

if (product){
    order.add_product(product, options);
}

Hope it helps

I found a solution, 
may pe it will help 

this code 

 

var product = this.env.pos.db.get_product_by_id(productId);
var order = this.env.pos.get_order();
if (product) {
    order.add_product(product);
} else {
    console.error("Error Not there");
}

put the problem if the productId belongs to one of the products in the order It's coming and if the productId does not belong to it's giving me undefined

can any one help me 

As an addition to the answers above, if the product is not loaded in the POS yet, we can load it first using this code

var product = this.env.pos.db.get_product_by_id(line.product_id);                    if (!product) {                        
    // If product is not loaded in POS, load it                       
    await this.env.pos._addProducts([line.product_id]);                       
    // Assume that the result is unique.                        
    product = this.env.pos.db.get_product_by_id(line.product_id);                    
}