Javascript Object - 21 Methods (Reference)

https://webdevfix.com/21-object-methods-in-javascript

Tech:

Javascript

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1 year ago

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In Javascript Object is a entity that can hold properties and methods. Basically, it is a collection of key-value pairs.

defineProperty()

Adds the named property described by a given descriptor to an object.

// Object.defineProperty(obj, prop, descriptor);

var obj = {};

Object.defineProperty(obj, '111', {
  value: "aaa",

  writable: false,
  enumerable: false,
  configurable: false
});

obj.111;
// aaa

defineProperties()

Adds the named properties described by the given descriptors to an object.

// Object.defineProperties(obj, props)

var obj = {};

Object.defineProperty(obj, {
  111 : {
    value: "aaa",
    writable: false,
    enumerable: false,
    configurable: false
  },
  222 : {
    value: "bbb",
    writable: false,
    enumerable: false,
    configurable: false
  }
});

obj.111;
// aaa

obj.222;
// bbb

getOwnPropertyDescriptor()

It returns a property descriptor for a named property on an object.

// Object.getOwnPropertyDescriptor(obj, prop)

var obj = {
  111: "aaa"
};

var x = Object.getOwnPropertyDescriptor(obj, "111");

// x = {
//  value: "aaa",
//  writable: true,
//  enumerable: true,
//  configurable: true
// }

getOwnPropertyDescriptors()

Returns an object containing all own property descriptors for an object.

// Object.getOwnPropertyDescriptors(obj)

var obj = {
  111: "aaa",
  222: "bbb"
};

var x = Object.getOwnPropertyDescriptors(object1);

// x = {
//  111 : {
//    value: "aaa",
//    writable: true,
//    enumerable: true,
//    configurable: true
//  },
//  222: {
//    value: "bbb",
//    writable: true,
//    enumerable: true,
//    configurable: true
//  }

getOwnPropertyNames()

Returns an array containing the names of all of the given object's own enumerable and non-enumerable properties.

// Object.getOwnPropertyNames(obj)

var obj = {
  111: "aaa",
  222: "bbb"
};

var x = Object.getOwnPropertyNames(obj);

// x = ["111", "222"]

getOwnPropertySymbols()

Returns an array of all symbol properties found directly upon a given object.

// Object.getOwnPropertySymbols(obj)

var obj = {};

obj[Symbol("a")] = "localSymbol";
obj[Symbol.for("b")] = "globalSymbol";

var x = Object.getOwnPropertySymbols(obj);

// x = [Symbol(a), Symbol(b)]

keys()

Returns an array containing the names of all of the given object's own enumerable string properties.

// Object.keys(obj)

var obj = {
  111: "aaa",
  222: "bbb"
};

var x = Object.keys(obj);

// x = ["111", "222"]

values()

Returns an array containing the values that correspond to all of a given object's own enumerable string properties.

// Object.values(obj)

var obj = {
  111: "aaa",
  222: "bbb"
};

var x = Object.values(obj);

// x = ["aaa", "bbb"]

getPrototypeOf()

Returns the prototype (internal [[Prototype]] property) of the specified object.

// Object.getPrototypeOf(obj)

var obj = {
  111: "aaa"
};
var x = Object.create(obj);

// x = { 111: "aaa" }

setPrototypeOf()

Sets the object's prototype (its internal [[Prototype]] property).

// Object.setPrototypeOf(obj, prototype)

const obj1 = {
  111: "aaa"
};
const obj2 = {
  111: "bbb"
};
Object.setPrototypeOf(obj1, obj2);
var x = Object.getPrototypeOf(obj1);

// x = { 111: "bbb" }

isExtensible()

Determines if extending of an object is allowed.

// Object.isExtensible(obj)

var obj = {
  111: "aaa"
};

var x = Object.isExtensible(obj);
// x = true

preventExtensions()

Prevents any extensions of an object.

// Object.preventExtensions(obj)

var obj = {
  111: "aaa"
};

Object.preventExtensions(obj);
var x = Object.isExtensible(obj);
// x = false

seal()

Prevents other code from deleting properties of an object.

// Object.seal(obj)

var obj = {
  111: "aaa"
};

Object.seal(obj);

// delete object1.111 cannot be done

isSealed()

Determines if an object is sealed.

// Object.isSealed(obj)

var obj = {
  111: "aaa"
};

var x = Object.isSealed(obj);

// x = false

freeze()

Freezes an object. Other code cannot delete or change its properties.

// Object.freeze(obj)

const obj = {
  111: "aaa"
};

Object.freeze(obj);

// delete object1.111 cannot be done
// object1.222 = "bbb" cannot be done

isFrozen()

Determines if an object was frozen.

// Object.isFrozen(obj)

var obj = {
  111: "aaa"
};

var x = Object.isFrozen(obj);

// x = false

is()

Compares if two values are the same value. Equates all NaN values (which differs from both Abstract Equality Comparison and Strict Equality Comparison).

// Object.is(value1, value2);

Object.is("foo", "foo"); // true
Object.is(window, window); // true

Object.is("foo", "bar"); // false
Object.is([], []); // false

var foo = { a: 1 };
var bar = { a: 1 };
Object.is(foo, foo); // true
Object.is(foo, bar); // false

Object.is(null, null); // true

// Special Cases
Object.is(0, -0); // false
Object.is(-0, -0); // true
Object.is(NaN, 0 / 0); // true

assign()

Copies the values of all enumerable own properties from one or more source objects to a target object.

  // Object.assign(target, source);

var obj1 = {
  111 : "aaa",
  222 : "bbb"
};
var obj2 = {
  222 : "BBB",
  333 : "ccc"
};

Object.assign(obj1, obj2);

// obj1 = {
  111 : "aaa",
  222 : "BBB",
  333 : "ccc"
}

create()

Creates a new object with the specified prototype object and properties.

// Object.create(proto, [propertiesObject]);

var obj1 = {
  111 : "aaa",
  222 : "bbb"
};

var x = Object.create(obj1);
x.333 = "ccc";

//  x = {
//   333 : "ccc"
//  }

x.333;
// ccc

x.__proto__.111;
// aaa

x.111;
// aaa

entries()

Returns an array containing all of the [key, value] pairs of a given object's own enumerable string properties.

// Object.entries(obj)

var obj = {
  111: "aaa",
  222: "bbb"
};

var x = Object.entries(obj);

// x = [["111", "aaa"], ["222", "bbb"]]

fromEntries()

Returns a new object from an iterable of [key, value] pairs.

// Object.fromEntries(iterable);

var arr = [
  ["111", "aaa"],
  ["222", "bbb"]
];

var x = Object.fromEntries(arr);

// x = {
//  111: "aaa",
//  222: "bbb"
// }