Naked objects in javascript part of ECMAScript standard?

Question

I came across this article , which suggests using bare objects for your hashmap needs if your keys are always strings.

Bare objects are objects created using nulla prototype value, for example, c Object.create(null). Using object notation (i.e. {}) does not create bare objects, since they are set as a prototype Object.prototype.

The article points out that the great thing about bare objects is that you can use them as hashmaps without worrying about built-in keys, such as toStringpotentially causing errors when using a key with the same name.

Is this part of the behavior of ES5 and / or ES6? That is, if I use bare objects as hash cards of string keys in my code, can I rely on my code behaving as I would expect? Are there any reservations here?

Answer 1

First of all, ECMA-Script 2015 and above has collections such as Map. That is, in new JavaScript implementations you no longer need to simulate dictionaries / hashmaps / hash tables with objects.

The article states that the great thing about bare objects is that you can use them as hashmaps without worrying about built-in objects such as toString, potentially causing errors when using a key with the same name.

, toString , , .

, , : var obj = { text: "Matias" };.

for..in Object.prototype, Object.keys :

Object.keys(obj).forEach(propertyName => {
    var someOwnProperty = obj[propertyName ];
});

, for..in Object.keys Object.prototype.hasOwnProperty:

for(var propertyName in obj) {
    if(obj.hasOwnProperty(propertyName)) {
       // True if property is declared on obj and not in some 
       // level of the prototype chain
    }
}

: @bergi -. obj hasOwnProperty, for..in , obj.hasOwnProperty Object.prototype.hasOwnProperty .

, , :

var obj = {
    hasOwnProperty: "hey! I'm not Object.prototype.hasOwnProperty anymore!"
};

hasOwnProperty Object.prototype.hasOwnProperty.

Object.prototype.hasOwnProperty Function.prototype.call:

for(var propertyName in obj) {
    if(Object.prototype.hasOwnProperty.call(obj, propertyName)) {
       // True if property is declared on obj and not in some 
       // level of the prototype chain
    }
}

Object.prototype.hasOwnProperty , if, this Function.prototype.bind:

var hasOwnProperty = Object.prototype.hasOwnProperty.bind(obj);

for(var propertyName in obj) {
    if(hasOwnProperty(propertyName)) {
       // True if property is declared on obj and not in some 
       // level of the prototype chain
    }
}

Object.create(null), , - :

var bareObject = Object.create(null, {
   text: { value: "hello world" }
});

var secondObject = Object.create(bareObject);
secondObject.text2 = "bye!";

for(var property in secondObject) {
   // WAIT, secondObject prototype is a bare object! 
   // And I can't call secondObject.hasOwnProperty to check
   // if the enumerated property is declared in the own object...    
}

, , in:

if("someProperty" in bareObject) {

} 

Object.prototype.hasOwnProperty Function.prototype.call Function.prototype.bind, .

, , ES2015 , BabelJS, JavaScript .

ES5 / ES6? , , , ? - ?

Object.create ECMA- Script 5. , - NodeJS.

Answer 2

ES5 / ES6?

. Object.create(null) / , ES5, ES6 ES7.

- , , ?

. , hashmaps, . .

ES6, Map, .