NodeJS sum the object values in the array-CodePudding

I have objects in the array. one of these objects references another template.

I want the price of the data in the reference template to be multiplied by the number in the array, and I want the result to be written to the total.

const debt = new Schema({
  name: {
    type: String,
    required: true,
  },
  medicine: [{

    data: {
      type: Schema.Types.ObjectId,
      ref: 'Medicine',
    },
    quantity: {
      type: Number,
      default: 1
    }
  }],
  total: {
    type: Schema.Types.Decimal128,
    default: 0,
  },
  status: {
    type: String,
    required: true,
  },
  createdAt: {
    type: Date,
    default: Date.now,
  },
});

const medicine = new Schema({
  name: {
    type: String,
    unique: true,
    required: true,
  },
  price: {
    type: Schema.Types.Decimal128,
    required: true,
  },
  medicineType: {
    type: String,
    required: true,
  },
  description: {
    type: String,
    required: true,
    trim: true,
  },
  image: {
    type: String,
  },
  createdAt: {
    type: Date,
    default: Date.now,
  },
});

When we create data from the two templates above, the result is as follows.

{
  name: 'John Doe',
  no: '87102621880',
  status: 'debtor',
  note: 'not paid',
  medicine: [
    { data: '624e0b9533533f3a31e3dc73', quantity: 2 },
    { data: '624e0b3633533f3a31e3dc6a', quantity: 3 }
  ],
  total: 0
}

In the above result, the total value is zero, but I want it like this.

total = data.price * medicine.quantity

I want to do this operation inside the pre method, is it possible or is there another way?

I hope I have been able to explain, if there is more than one value in the medicine array, all of them (data.price * medicine.quantity) should do the same and transfer them to the total value.

CodePudding user response：

You can define mongoose middleware to run pre/post some actions in the schema.

debtSchema.post('find',(results)=>{//do whatever you want here, it'll run every time you're querying by the 'find' method and you have access to the results})

Here's link to the official docs

CodePudding user response：

use Array.prototype.reduce() https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce

const a = {
  name: 'John Doe',
  no: '87102621880',
  status: 'debtor',
  note: 'not paid',
  price: 5,
  medicine: [
    { data: '624e0b9533533f3a31e3dc73', quantity: 2, price: 5 },
    { data: '624e0b9533533f3a31e3dc73', quantity: 1, price: 3 },
    { data: '624e0b3633533f3a31e3dc6a', quantity: 3, price: 6 },
  ],
  total: 0,
}

console.log(
  a.medicine.reduce(
    (previousValue, currentValue) =>
      previousValue   currentValue.quantity * currentValue.price,
    0,
  ),
)

// if price is in different object

console.log(
  a.medicine.reduce(
    (previousValue, currentValue) =>
      previousValue   currentValue.quantity * a.price,
    0,
  ),
)

// or just get count and then multiply by price
console.log(
  a.medicine.reduce(
    (previousValue, currentValue) =>
      previousValue   currentValue.quantity,
    0,
  ) * a.price,
)

Edit: eddited mistake in snipper where it was adding instead of multiplying