How to create a query that finds the values in between 2 numbers which are of type string in MongoDB

Question

Im actually new to MongoDB, I need to create a query that could find values in between 10 and 500 in 'quantity' field. But the 'quantity' is of type string .

The below code snipet shows my Inventory Model(which contains the quantity field of type string)

const inventorySchema = mongoose.Schema({
  email: {type: String , require:true},
  name: {type: String , require:true},
  quantity: {type: String , require:true}, //The quantity field is of type string
  batchId: {type: String , require:true},
  expireDate: {type: Date , require:true},
  price: {type: String , require:true},
  imagePath : { type: String , require: true}
}) 

I used the below mongoDB expression query using $lte and $gte operations but this didn't work . It gave me an error stating "An object representing an expression must have exactly one field"

    const postQuery = Inventory.find({ $expr: { 
                                       $lte: [ { $toDouble: "$quantity" }, 500.0 ],
                                       $gte: [ { $toDouble: "$quantity" }, 10.0 ] }
                                     });

Answer 1

Yes because $expr support one expression field at a time, you can try this way,

Inventory.find({ 
    $and:[
    // GT FIRST
    {$expr: {  $gte: [ { $toDouble: "$quantity" }, 10.0 ] } },
    // LT LAST
    {$expr: { $lte: [ { $toDouble: "$quantity" }, 500.0 ]} }
    ]
});

With $and we can use 2 separate expressions