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Creating a transformer

What you'll learn
  • Creating custom functional (unidirectional) transformers
  • Creating custom object (bidirectional) transformers

Functional transformer​

The functional (or unidirectional) transformer is a simple function which transform a raw value to its real counterpart.

Here is an example of functional transformer with the Foscia's toNumber transformer.

function toNumber() {
    return (value: unknown) =>
        value === undefined || value === null || value === ''
            ? undefined
            : Number(value);
}

Object transformer​

The object (or bidirectional) transformer has two functions to transform values:

  • serialize which converts a real value to its raw counterpart
  • deserialize which converts a raw value to its real counterpart

Here is an example of functional transformer with the Foscia's toDate transformer.

function toDate() {
    return {
        serialize(value: Date | undefined) {
            return value?.toISOString();
        },
        deserialize(value: unknown) {
            if (typeof value === 'string') {
                const date = new Date();
                date.setTime(Date.parse(value));

                return date;
            }

            return undefined;
        },
    };
}