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@cookbook/mapper-js
Advanced tools
Fast, reliable and intuitive object mapping.
Play around with mapper-js and experience the magic!
npm install @cookbook/mapper-js --save
#or
yarn add @cookbook/mapper-js
Before we start, it is essential that we know your data structure so we can map it accordingly.
For this demo case, let's assume that we have the following object:
const source = {
person: {
name: {
firstName: 'John',
lastName: 'Doe',
},
age: 32,
drinks: ['beer', 'whiskey'],
address: [
{
street: 'Infinite Loop',
city: 'Cupertino',
state: 'CA',
postalCode: 95014,
country: 'United States',
},
{
street: '1600 Amphitheatre',
city: 'Mountain View',
state: 'CA',
postalCode: 94043,
country: 'United States',
},
],
},
};
At this step, we need to create our mapping
against our data source
.
We will be using dot notation
to create our final structure
.
For more info about
dot notation
API, check out the documentation
With mapper
, it is possible to get
one or several values from our source
and even transform
it in the way we need.
For that, map()
accepts single dot notation
path or
an array of dot notation paths
. E.g.: map('person.name.firstName')
, map([person.name.firstName, person.name.lastName]);
'
Those values can be transformed by using the .transform()
method, which expects a function
as argument and provides
the selected values as array in the parameter
.
For more information about the usage, check the API Documentation.
Now let's create our mapping
!
// mapping.ts
import mapper from '@cookbook/mapper-js';
...
const mapping = mapper((map) => ({
'person.name': map('person.name')
.transform(({ firstName, lastName }) => `${firstName} ${lastName}`)
.value,
'person.lastName': map('person.lastName').value,
'person.isAllowedToDrive': map(['person.age', 'person.drinks'])
.transform((age, drinks) => age > 18 && drinks.includes('soft-drink'))
.value,
address: map('person.address').value,
defaultAddress: map('person.address[0]').value,
}));
import mapping from './mapping';
...
const result = mapping(source);
/* outputs
{
person: {
name: 'John Doe',
isAllowedToDrive: false,
},
address: [
{
street: 'Infinite Loop',
city: 'Cupertino',
state: 'CA',
postalCode: 95014,
country: 'United States'
},
...
],
defaultAddress: {
street: 'Infinite Loop',
city: 'Cupertino',
state: 'CA',
postalCode: 95014,
country: 'United States'
}
}
*/
Type: function()
Parameter: mapping: Mapping
Return: <T>(source: object | object[], options?: Options) => T extends [] ? T[] : T
,
Signature: (mapping: Mapping) => <T>(source: object | object[], options?: Options) => T extends [] ? T[] : T
Description:
mapper()
is the main method and responsible for mapping the values from your data source against the mapping instructions.
It accepts dot notation
path(s) as key(s)
.
Example:
// raw definition
const mapping = mapper((map) => ({
...
}));
// with map() query
const mapping = mapper((map) => ({
'employee.name': map('person.name.firstName').value,
'employee.age': map('person.name.age').value,
'employee.address': map('person.address').value,
}));
As a result from the above implementation, mapper()
return a new function
to map and compile your source data against your mapping.
It accepts an extra (optional) argument defining the global mapping options.
Example:
...
mapping(source, options);
/* outputs
{
employee: {
name: 'John',
age: 32,
address: [
{
street: 'Infinite Loop',
city: 'Cupertino',
state: 'CA',
postalCode: 95014,
country: 'United States'
},
...
],
},
}
*/
Type: function
Parameter: keys: string | string[], options?: Options
Return: MapMethods<T>
,
Signature: <T = unknown>(keys: string | string[], options?: Options) => MapMethods<T>
Description:
root
method retrieves values from your source data using dot notation
path, it accepts a string or array of string.
It accepts an extra (optional) argument to define the mapping options for current entry, overriding the global mapping options.
Example:
map('person.name.firstName');
map(['person.name.firstName', 'person.name.lastName']);
map(['person.name.firstName', 'person.name.lastName'], options);
transform
Type: function
Parameter: ...unknown[]
Return: unknown | unknown[]
,
Signature: (...args: unknown[]) => unknown | unknown[]
Description:
.transform
method provides you the ability to transform the retrieved value(s) from map()
according to your needs, and for that, it expects a return value.
.transform
provides you as parameter, the retrieved value(s) in the same order as defined in the map()
method, otherwise
Example:
// single value
map('person.name.firstName').transform((firstName) => firstName.toLoweCase());
// multiple values
map(['person.name.firstName', 'person.name.lastName']).transform((firstName, lastName) => `${firstName} ${lastName}`);
value
Type: readonly
Return: T
Description:
.value
returns the value of your dot notation
query. If transformed, returns the transformed value.
Example:
// single value
map('person.name.firstName').transform((firstName) => firstName.toLoweCase()).value;
// multiple values
map(['person.name.firstName', 'person.name.lastName']).transform((firstName, lastName) => `${firstName} ${lastName}`)
.value;
{
omitNullUndefined: false,
omitStrategy: () => false,
}
omitNullUndefined
Type: boolean
default value: false
Description:
Removes null
or undefined
entries from the mapped object.
Example:
/* source object
{
person: {
name: 'John',
lastName: 'Doe',
age: 32,
},
}
*/
const mapping = mapper((map) => ({
name: map('person.name').value,
age: map('person.age').value,
// source doesn't have property 'address',
// therefore will return "undefined"
address: map('person.address').value,
}));
mapping(source, { omitNullUndefined: true });
/* outputs
{
name: 'John',
age: 32,
}
*/
omitStrategy
Type: function
Parameter: value: unknown | unknown[]
Return: boolean
Signature: (value: unknown | unknown[]) => boolean
Description:
Defines a custom strategy to omit (suppress) entries from the mapped object.
Example:
/* source object
{
person: {
name: 'John',
lastName: 'Doe',
age: 32,
address: {
street: 'Infinite Loop',
city: 'Cupertino',
state: 'CA',
postalCode: 95014,
country: 'United States',
}
},
}
*/
const customOmitStrategy = (address: Record<string, string>): boolean => address && address.city === 'Cupertino';
const mapping = mapper((map) => ({
name: map('person.name').value,
age: map('person.age').value,
address: map('person.address').value,
}));
mapping(source, { omitStrategy: customOmitStrategy });
/* outputs
{
name: 'John',
age: 32,
}
*/
FAQs
Fast, reliable and intuitive object mapping.
We found that @cookbook/mapper-js demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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