object-assign-properties

curried and reusable function define object properties like Object.defineProperties

Usage & Arguments

objectAssignProperties(descriptor[, properties[, object]])

((descriptor, properties, object) => *) => descriptor => properties => object => object

there are 3 arguments of this curried function.

• descriptor description for properties (description)

• properties properties with it's value

• object target object

example

const objectAssignProperties = require("object-assign-properties");

const objectAssignPropertiesReadonly = objectAssignProperties({
    writable:false,
    configurable:false
})

getter/setter

getter and setter description would be little different from built-in ones

because of objectAssignProperties always assign mutable properties for mutable objects, so we need more property infos in our accessor functions

you can define getter and setter like this example below:

const objectAssignProperties = require("object-assign-properties");

const objectAssignPropertiesWithAccessor = objectAssignProperties({
   get(lastValue, key, self) { // inital or last value will save in a interal scope
       return lastValue + 1;
   }
   set(lastValue, newValue, prop, self) {
       if (typeof newValue === "number") {
          return newValue; // return value would be set as a new value for the property
       } else {
          return lastValue;
       }
   }
})

Example

normal description

const objectAssignProperties = require("object-assign-properties");

let target = {};

objectAssignProperties({
    writable:false,
    configurable:false
}, {
    a:1
    b:2
}, target);

console.log(target); // assign readonly properties `a` `b` `c` to target object

normal description (curry)

const objectAssignProperties = require("object-assign-properties");

const objectAssignPropertiesReadonly = objectAssignProperties({
    writable:false,
    configurable:false
});

const objectAssignPropertiesReadonlyABC = objectAssignPropertiesReadonly({
    a:1, b:2, c:3
})

let target1 = {};
let target2 = {};

objectAssignPropertiesReadonlyABC(target1); // assign readonly properties `a` `b` `c` to target object
objectAssignPropertiesReadonlyABC(target2);

accessor description (getter and setter)

const objectAssignProperties = require("object-assign-properties");

const objectAssignPropertiesGetPlus1 = objectAssignProperties({
    get(value, key){
        return value + 1;
    }
}, {
    a:1, b:2, c:"c"
})

let target1 = {};
let target2 = {};

objectAssignPropertiesGetPlus1(target1);
objectAssignPropertiesGetPlus1(target2);

console.log(target1.a) // 2;
console.log(target1.b) // 3;
console.log(target1.c) // "c1";

console.log(target2.a) // 2;
console.log(target2.b) // 3;
console.log(target2.c) // "c1";

Benchmark (nodejs v7.3.0 | macOS | 2.2 GHz Intel Core i7)

Benchmark sources can be found in the folder

1.create assign properties for object

assign a,b,c, with enumerable:false and writable:false

function \ ops/sec	create
Object.defineProperties	530,060
object-assign-properties	223,242
object-assign-properties curry 1 argument	219,352
object-assign-properties curry 2 arguments	215,466

2.call assigned properties with accessor (getter and setter)

assigned a property with getter and setter, then object[property] = object[property] + 1

function \ ops/sec	call first object	call second object	call third object
object-assign-properties	60,629,790	27,843,142	26,903,146
Object.defineProperties	77,280,414	3,825,480	3,832,452

why object-assign-properties performance better after the first object ?

reference issue nodejs/help|#442

objects with the same property name and different function defined via accessor (getter/setter) (even with the same return value) are always turned to dictionary mode expect the first one, however if we always define same function for accessor of the same property name, then the object will stay fast!

Reference

• MDN | Object.defineProperty

dependencies

• fast-curry