HasProperty

A method to determine whether an object has a property with the specified property key. The property may be either an own or inherited. This method follows ECMAScript's specification for the 'HasProperty' abstract operation.

Currently, this module only supports the ES2017 (ES8) specification.

Why?

While working on a module, I found myself with a need to reproduce ECMAScript internal methods and abstract operations. I wanted smaller, modular code instead of a larger library.

Installation Using npm

npm install es-abstract-has-property

Example Usage

var hasProperty = require('es-abstract-has-property');

function Animal(obj){
  this.animalInstanceMethod_A = function alfa(a) {}
  this.init.apply(this, arguments)
}
Animal.prototype.init = function animalInit() {
  this.animalInstanceMethod_B = function bravo(b) {}
}
Animal.animalStaticMethod = function charlie(c) {}
Animal.prototype.animalPrototypeMethod = function delta(d) {}

function Cat(){
  this.init.apply(this, arguments)
}
Cat.prototype = Object.create(Animal.prototype)
Cat.prototype.constructor = Cat
Cat.prototype.init = function catInit() {
  Animal.prototype.init.call(this)
  this.catInstanceMethod = function echo(e) {}
}

var c = new Cat()
console.log(c.hasOwnProperty("animalPrototypeMethod")) // => false
console.log(hasProperty(c, "animalPrototypeMethod"))   // => true
console.log(hasProperty(c, "animalInstanceMethod_A"))  // => false
console.log(hasProperty(c, "animalInstanceMethod_B"))  // => true
console.log(hasProperty(c, "animalStaticMethod"))      // => false

Documentation

• API
• ECMAScript Specification References

API

HasProperty(O, P)

Determine whether an object has a property with the specified property key. The property may be either an own or inherited.

A Boolean value is returned.

O

Type: Object

The object being checked. Values will be coerced using Object(O), allowing for the checking of properties such as "length" on a string primitive.

P

Type: String

The property key to look for on the object.

Related Projects

• es-abstract: a single library for multiple ECMAScript abstract operations.