How to add a custom DataType in Sequelize ORM

Question

I want to define a custom data type in Sequelize by inheriting all default behaviours of existing DataType.Integer. The base idea here is to define a new type and override valueOf and toString methods.

The Sequelize docs doesn't contain any information related to this topic. It would be really nice if someone can help me on this.

Answer 1

https://github.com/sequelize/sequelize/blob/master/lib/data-types.js holds the sequelize data types.

Specifically, https://github.com/sequelize/sequelize/blob/master/lib/data-types.js#L251-L273 shows how DataTypes.INTEGER inherits from DataTypes.NUMBER using NUMBER.inherits(fn).

Those inherit from ABSTRACT. You could override the toString() method for your inherited data type like as seen at https://github.com/sequelize/sequelize/blob/master/lib/data-types.js#L62-L64.

Disclaimer: with it not being publicly documented, I am not sure how stable the APIs are and would be cautious due to possible future changes.

Answer 2

To extend DataTypes in Sequelize:

class DataTypes_IP extends DataTypes.ABSTRACT {
  constructor () {
    super()
    this.key = 'IP'
  }

  toSql() {
    return 'VARBINARY(16)'
  }

  // Todo
  validate (value) {
    // const Validator = require('./utils/validator-extras').validator 
    // if (!Validator.isDate(String(value))) {
    //   throw new sequelizeErrors.ValidationError(util.format('%j is not a valid date', value)) 
    // }
    return true 
  }

  _sanitize (value) {
    return new IP(value) 
  } 

  _isChanged (value, originalValue) {

    if (value === originalValue) return false
    if (
      value instanceof IP && 
      originalValue instanceof IP && 
      value.toBuffer().equals(originalValue.toBuffer()) 
      ) {
      return false
    }
    return true
  } 

  _stringify (ip) {
    return ip.toBuffer() 
  } 
}

And extends the DataTypes

DataTypes.IP = DataTypes_IP

You can check the relevant issue in github. https://github.com/sequelize/sequelize/issues/8533