@jhel/om v1.2.0
Object Mapper
Utility that adds composable utility methods to map a complecated nested object to a flat controlled destination object.
Applications
When integrating towards external api's it is common to get complicated nullable object structures that can result in error prone mapping of said objects.
This utility will help map and return properties in nested objects making it easier to then use in an application.
Install
Via yarn
yarn add @jhel/om
Via npm
npm install @jhel/om
Api
Keypath
An essential part of the API is the keypath
. A keypath
is a dot notated string path that resembles the path to get to the specific property.
For example the keypath foo.bar.value
would retreive the value of the value
prop in the object:
{
foo: {
bar: {
value: any; // <--- The value
}
}
}
Operators
Every method is composable meaning they can be combined with each other to create more complex structures.
Take
Takes a specific property value from an object by given keypath
.
If the object does not have the value specified in the keypath (or along the path), it will return null
@returns: Operator
Example:
const takeBarValue = take('foo.bar.value');
const theValue = takeBarValue({
foo: { bar: { value: 'The returned value' } }
}); // returns "The returned value"
Either
Supply it with an arbitraty amount of Operator
values, it will return the first defined value from the supplied Operator
's.
@returns: Operator
Example:
const takeOopsValue = take('foo.bar.oops');
const takeBarValue = take('foo.bar.value');
const takeEitherOopsOrBarValue = either(takeOopsValue, takeBarValue);
const theValue = takeEitherOopsOrBarValue({
foo: { bar: { value: 'The returned value' } }
}); // returns "The returned value"
When
If first operator is truthy it will return the value from the second Operator
otherwise null.
@returns: Operator
const takeTypename = take('__typename');
const takeBarValue = take('foo.bar.value');
const whenBarTakeBarValue = when(takeTypename, takeBarValue);
const theValue = whenBarTakeBarValue({
__typename: 'BAR',
foo: { bar: { value: 'The returned value' } }
}); // return "The returned value"
ValueIs
First operator strictly checks with given value or runs a given predicate, return true
or false
depending on outcome.
@returns: Operator
const takeTypename = take('__typename');
const isTypenameBar = valueIs(takeTypename, 'BAR');
const isTypenameNotBar = valueIs(
takeTypename,
(typename) => typename !== 'BAR'
);
isTypenameBar({
__typename: 'BAR',
foo: { bar: { value: 'The returned value' } }
}); // return true
isTypenameNotBar({
__typename: 'BAR',
foo: { bar: { value: 'The returned value' } }
}); // return false
Om
Allows to create a new object using a supplied schema.
@return: Operator
const mapObject = om({
value: take('foo.bar.value')
foo: om({
bar: when(take('__typename'), take('foo.bar'))
})
})
const returnObject = mapObject({ __typename: 'BAR', foo: { bar: { value: 'The returned value' } } })
console.log(returnObject) // { value: 'The returned value', foo: { bar: { value: 'The returned value' } } }