REVIEW: Javascript S.A. Study Guide > Objects > Flashcards

Objects Flashcards

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1
Q

var person = {
name : “steve”,
age : 24,
}

two ways to access

A

person[‘name’]

person.name

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2
Q

var person = {
name : “steve”,
age : 24,
}

set name to “bob”

A 
person.name = "bob"
person["name"] = "bob"
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3
Q

var person = {
name : “steve”,
age : 24,
}

add country Brazil

A 
person.country = "Brazil"
person["country'] = "Brazil"
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4
Q

let user = { name: “John”, age: 30 };

alert( “age” ________); // true, user.age exists

A

in user

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5
Q 
let user = {
  name: "John",
  age: 30,
  isAdmin: true
};

for (let key in user) {

alert( key ); //

}

A

name, age, isAdmin

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6
Q 
let user = {
  name: "John",
  age: 30,
  isAdmin: true
};

for (let key in user) {

alert( user[key] ); //
}

A

John, 30, true

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7
Q 
let codes = {
  "49": "Germany",
  "41": "Switzerland",
  "44": "Great Britain",
  // ..,
  "1": "USA"
};

for (let code in codes) {
alert(code); //
}

A

1, 41, 44, 49

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8
Q 
let codes = {
  "+49": "Germany",
  "+41": "Switzerland",
  "+44": "Great Britain",
  // ..,
  "+1": "USA"
};

for (let code in codes) {
alert( code ); //
}

A

49, 41, 44, 1

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9
Q

in objects ____________ properties are sorted, others appear in creation order.

A

integer

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10
Q 
let a = {};
let b = {};

alert( a == b ); //

A

false

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11
Q

An object declared as const can or cannot be changed.

A

can

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12
Q

let user = { name: “John”, age: 30 };

alert( “blabla” in user ); //

A

false, user.blabla doesn’t exist

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13
Q 
let a = {};
let b = a;

alert( a == b );

A

true

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14
Q 
let a = {};
let b = a;

alert( a === b ); //

A

true

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15
Q 
let a = {};
let b = {};
alert( a == b ); //
A

false

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16
Q

We also can use ____________ to replace the loop for simple cloning:

A

Object.assign

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17
Q 
let user = {
  name: "John",
  age: 30
};

Clone using Object.assign

A

let clone = object.assign({}, user);

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18
Q 
let user = {
  name: "John",
  sizes: {
    height: 182,
    width: 50
  }
};

alert( user.sizes.height ); //

A

182

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19
Q 
let user = {
  name: "John",
  sizes: {
    height: 182,
    width: 50
  }
};

alert( _________ ); //50

A

user.sizes.width

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20
Q

The object constructor, which uses the______ keyword

A

new

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21
Q

ADD NEW METHOD NAMED “COLOR”

let user = {
  name: "John",
  age: 30
};
A 
user.color = function() {
 //code
}
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22
Q 
// Initialize an object
const employees = {
    boss: 'Michael',
    secretary: 'Pam',
    sales: 'Jim',
    accountant: 'Oscar'
};

// Get the keys of the object
const keys = \_\_\_\_\_\_\_\_(employees);

console.log(keys);

A

object.keys

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23
Q 
let user = {
name: "John", 
age: 30, 
isAdmin: true 
};

for (let key in user) {
alert(________);
} name, age, isAdmin

A

key

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24
Q 
let user = {
name: "John", 
age: 30, 
isAdmin: true 
};

for (let key in user) {
alert(________);
} john, 30, true

A

user[key]

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25
``` const job = { position: 'cashier', type: 'hourly', isAvailable: true, }; ``` ``` // const barista = //create a new JOB object ```
Object.create(job);
26
The ___________ method creates a new object, using an existing object as the prototype of the newly created object.
Object.create()
27
The ___________ method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.
Object.assign()
28
a _______ is something you can do with an object
method
29
The _______ determines if an object is frozen.
Object.isFrozen()
30
``` const object1 = { property1: 42 }; ``` ``` console.log(Object.isFrozen(object1)); // expected output: ```
false
31
``` const object1 = { property1: 42 }; ``` ``` console.log(Object.isFrozen(object1)); // expected output: false ``` Object.freeze(object1); ``` console.log(Object.isFrozen(object1)); // expected output: ```
true
32
``` const obj = { prop: 42 }; ``` Object.freeze(obj); ``` obj.prop = 33; // ```
Throws an error in strict mode
33
The __________ method freezes an object. A frozen object can no longer be changed; freezing an object prevents new properties from being added to it, existing properties from being removed, prevents changing the enumerability, configurability, or writability of existing properties, and prevents the values of existing properties from being changed.
Object.freeze()
34
The __________method seals an object, preventing new properties from being added to it and marking all existing properties as non-configurable. Values of present properties can still be changed as long as they are writable.
Object.seal()
35
``` const object1 = { property1: 42 }; ``` Object.seal(object1); object1.property1 = 33; console.log(object1.property1); // expected output: -------------> ``` delete object1.property1; // ------> console.log(object1.property1); // expected output: ---------> ```
33 33
36
The__________ method determines if an object is sealed.
Object.isSealed()
37
``` const object1 = { property1: 42 }; ``` ``` console.log(Object.isSealed(object1)); // expected output: ``` Object.seal(object1); ``` console.log(Object.isSealed(object1)); // expected output: ```
false true
38
The ___________ method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.
Object.assign()
39
``` const target = { a: 1, b: 2 }; const source = { b: 4, c: 5 }; ``` const returnedTarget = Object.assign(target, source); ``` console.log(target); // expected output: ``` ``` console.log(returnedTarget); // expected output: ```
Object { a: 1, b: 4, c: 5 } Object { a: 1, b: 4, c: 5 }
40
The_________ method returns an array of a given object's own property names, in the same order as we get with a normal loop.
Object.keys()
41
``` const object1 = { a: 'somestring', b: 42, c: false }; ``` ``` console.log(Object.keys(object1)); // expected output: ```
Array ["a", "b", "c"]
42
``` const object1 = { a: 'somestring', b: 42, c: false }; ``` ``` console.log(__________(object1)); // expected output: Array ["a", "b", "c"] ```
``` const object1 = { a: 'somestring', b: 42, c: false }; ``` ``` console.log(Object.keys(object1)); // expected output: Array ["a", "b", "c"] ```
43
``` var arr = ['a', 'b', 'c']; console.log(Object.keys(arr)); // console: ```
['0', '1', '2']
44
``` var obj = { 0: 'a', 1: 'b', 2: 'c' }; console.log(Object.keys(obj)); // console: ```
['0', '1', '2']
45
``` var anObj = { 100: 'a', 2: 'b', 7: 'c' }; console.log(Object.keys(anObj)); // console: ```
['2', '7', '100']
46
``` var anObj = { "+100": 'a', "+2": 'b', "+7": 'c' }; console.log(Object.keys(anObj)); // console: ```
['100', '2', '7']
47
The________ method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).
Object.values()
48
``` const object1 = { a: 'somestring', b: 42, c: false }; ``` ``` console.log(Object.values(object1)); // expected output: ```
Array ["somestring", 42, false]
49
``` const object1 = { a: 'somestring', b: 42, c: false }; ``` ``` console.log(_____________); // expected output: Array ["somestring", 42, false] ```
(Object.values(object1)
50
The _____ determines if an object is frozen.
The Object.isFrozen() determines if an object is frozen.
51
``` const object1 = { property1: 42 }; ``` ``` console.log(Object.isFrozen(object1)); // expected output: ------------> ``` Object.freeze(object1); ``` console.log(Object.isFrozen(object1)); // expected output: ----------------> ```
false true
52
The _______method returns a string representing the source code of the function.
toString()
53
``` function sum(a, b) { return a + b; } console.log(sum.toString()); // expected output: -------> ```
"function sum(a, b) { | return a + b};
54
``` function sum(a, b) { return a + b; } ``` ``` console.log(___________); // expected output: "function sum(a, b) { // return a + b; // }" ```
sum.toString());
55
The _________ method determines if an object is extensible (whether it can have new properties added to it).
Object.isExtensible()
56
const object1 = {}; ``` console.log(Object.isExtensible(object1)); // expected output: ```
true
57
``` // New objects are extensible. var empty = {}; ``` TRUE/FALSE
TRUE
58
``` var sealed = Object.seal({}); Object.isExtensible(sealed); // === ``` TRUE/FALSE
false
59
TRUE/FALSE ``` var frozen = Object.freeze({}); Object.isExtensible(frozen); // === ```
false
60
``` function Dog(name) { this.name = name; } ``` var dog1 = new Dog('Gabby'); Dog.prototype.toString = function dogToString() { return '' + this.name; } ``` console.log(dog1.toString()); // expected output: ```
"Gabby"
61
The __________method checks if an object exists in another object's prototype chain.
isPrototypeOf()
62
``` function object1() {} function object2() {} ``` ``` const object3 = new object1(); console.log(object2.prototype.isPrototypeOf(object3)); ```
false
63
``` function object1() {} function object2() {} ``` object1.prototype = Object.create(object2.prototype); const object3 = new object1(); ``` console.log(object1.prototype.isPrototypeOf(object3)); // expected output: ---------> ``` ``` console.log(object2.prototype.isPrototypeOf(object3)); // expected output: ----------> ```
true true
64
The ____________ method returns a boolean indicating whether the object has the specified property as its own property (as opposed to inheriting it).
hasOwnProperty()
65
``` const object1 = new Object(); object1.property1 = 42; ``` ``` console.log(object1.hasOwnProperty('property1')); // expected output: ```
true
66
``` const object1 = new Object(); object1.property1 = 42; ``` ``` console.log(object1.hasOwnProperty('toString')); // expected output: ```
false
67
``` const object1 = new Object(); object1.property1 = 42; ``` ``` console.log(object1.hasOwnProperty('hasOwnProperty')); // expected output: ```
false
68
hasOwnProperty returns true even if the value of the property is_____ or________.
null undefined
69
o = new Object(); o. propOne = null; o. hasOwnProperty('propOne'); // returns o. propTwo = undefined; o. hasOwnProperty('propTwo'); // returns
true true
70
o = new Object(); o. hasOwnProperty('prop'); // returns o. prop = 'exists'; o. hasOwnProperty('prop'); // returns
false | true
71
o = new Object(); o. prop = 'exists'; o. hasOwnProperty('prop'); // returns
true
72
o = new Object(); o. prop = 'exists'; o. hasOwnProperty('toString'); // returns
false
73
``` const prototype1 = {}; const object1 = Object.create(prototype1); ``` ``` console.log(Object.getPrototypeOf(object1) === prototype1); // expected output: ```
true
74
``` var proto = {}; var obj = Object.create(proto); Object.getPrototypeOf(obj) === proto; // ```
true
75
``` function sayHello2(name) { var text = 'Hello ' + name; // Local variable var say = function() { console.log(text); } return say; } var say2 = sayHello2('Bob'); say2(); // logs ```
"Hello Bob"
76
``` function say667() { // Local variable that ends up within closure var num = 42; var say = function() { console.log(num); } num++; return say; } var sayNumber = say667(); sayNumber(); // ```
logs 43
77
Without using new keyword how we could use these functions. So JavaScript has 3 different ways to do that:
1. call the function as a regular function 2. attach them to an object, as its properties 3. Use this, which is using call or apply to invoke the function
78
The ______method calls a function with a given this value and arguments provided as an array (or an array-like object).
apply()
79
The_________ method calls a function with a given this value and arguments provided individually.
call()
80
``` const object1 = new Object(); object1.property1 = 42; ``` console.log(Object.prototype.hasOwnProperty('hasOwnProperty'));
TRUE
REVIEW: Javascript S.A. Study Guide
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