linq2js / mapez

Map source object into destination object with ease

mapez

Map source object into destination object with ease

Installation

    npm i mapez

or

    yarn add mapez

Usage

ES6

import mapez from "mapez";
const result = mapez(source, spec);

CommonJS

const mapez = require("mapez/dist");
const result = mapez(source, spec);

A spec object key is the destination object key, and the value is selected value of the source object.

Map source object property to destination object property

const source = { foo: 1 };
const spec = {
  bar:
    // select foo value from source
    "foo",
};
const result = mapez(source, spec);
/*
    The result is
    {
        bar: 1
    }
 */

Nested mapping

const source = {
  name: "Box",
  width: 100,
  height: 100,
  category: { name: "Misc" },
};
const spec = {
  name: "name",
  // map category.name to category
  category: "category.name",
  // map width and height to dimension object
  dimension: {
    width: "width",
    height: "height",
  },
};
const result = mapez(source, spec);
/*
    The result is
    {
        name: 'Box',
        category: 'Misc',
        dimension: {
            width: 100,
            height: 100
        }
    }
 */

Using transformer

const source = { foo: 1 };
const spec = {
  visible: () => true,
  bar: (source) => source.foo * 2,
};
const result = mapez(source, spec);
/*
    The result is
    {
        visible: true,
        bar: 2
    }
 */

Using transformer with selectors

const source = { a: 1, b: 2 };
const spec = {
  sum: [
    // select a and b values from source
    "a",
    "b",
    // retrieve a and b values as transformer arguments
    (a, b) => a + b,
  ],
};
const result = mapez(source, spec);
/*
    The result is
    {
        sum: 3
    }
 */

Extending destination object properties

const source = {
  name: "Box",
  dimention: { data: { width: 100, height: 100 } },
  description: {
    data: { shortDescription: "hello", longDescription: "world" },
  },
};
const spec = { name: "name", "*": ["dimension.data", "description.data"] };
const result = mapez(source, spec);
/*
    The result is
    {
        name: 'Box',
        width: 100,
        height: 100,
        shortDescription: 'hello',
        longDescription: 'world'
    }
 */

Syntactic sugar

Selecting source object

"*";

Selecting property

"propertyName";

Selecting nested property

"level1Property.level2Property";

Selecting specified properties

Indicate included properties

"dimension>width|height";
// source: { dimension: { width: 0, height: 0, depth: 0 } }
// value: { width: 0, height: 0 }

Indicate excluded properties

"dimension!width|height";
// source: { dimension: { width: 0, height: 0, depth: 0 } }
// value: { depth: 0 }

Advanced Usage

You can use multiple transformers in a row, the first transformer retrieves all selected values as arguments, the following transformer receives the result of the previous transformer as an argument

const classyGreeting = (firstName, lastName) =>
  "The name's " + lastName + ", " + firstName + " " + lastName;
const toUpper = (string) => string.toUpperCase();
const source = {
  firstName: "James",
  lastName: "Bond",
};
const spec = [
  "firstName",
  "lastName",
  // classyGreeting retrieves firstName and lastName from selectors
  classyGreeting,
  // toUpper retrieves result of classyGreeting
  toUpper,
];
const result = mapez(source, spec);
// result: "THE NAME'S BOND, JAMES BOND"