250 Câu hỏi trắc nghiệm Javascript, CSS, HTML có đáp án

A.  for (biến = Giá trị đầu; Điều kiện; Giá trị tăng)

B.  for (biến = Giá trị đầu; Giá trị tăng; điều kiện)

C.  for (biến = Điều kiện; Giá trị tăng; Giá trị cuối)

D.  Tất cả các dạng trên.

A.  if (i != 5)

B.  if i =! 5 then

C.  if i <> 5

D.  if (i <> 5)

var a = [1, 2, 3];
var b = [1, 2, 3];
var c = '1,2,3';

console.log(a == c);
console.log(b == c);
console.log(a == b);

A. true, true, false

B. true, true, true

C. true, false, false

D. false, false false

var a = [9];
var b = [10];

console.log(a == 9);
console.log(b == 10);
console.log(a < b);

A. true true true

B. false false false

C. true true false

D. false false true

let i = 0;

const arr = new Array(5);
arr.forEach(() => i++);

console.log(i);

A. 0

B. 1

C. 4

D. 5

function greatestNumberInArray(arr) {
  let greatest = 0;
  for (let i = 0; i < arr.length; i++) {
    if (greatest < arr[i]) {
      greatest = arr[i];
    }
  }
  return greatest;
}

A. Yes

B. No

const arr = [1, 2, 3];

const a = arr.reduce(
  (acc, el, i) => ({ ...acc, [el]: i }),
  {}
);

const b = {};
for (let i = 0; i < arr.length; i++) {
  b[arr[i]] = i;
}

A. a

B. b

const arr = [
  x => x * 1,
  x => x * 2,
  x => x * 3,
  x => x * 4
];

console.log(arr.reduce((agg, el) => agg + el(agg), 1));

A. 1

B. 60

C. 100

D. 120

const ar = [5, 1, 3, 7, 25];
const ar1 = ar;
console.log(ar1.sort());
([5, 25].indexOf(ar[1]) != -1 &&
	console.log(ar.reverse())) ||
(ar[3] == 25 && console.log(ar));
console.log(ar1);

A. [1, 3, 5, 7, 25] [7, 5, 3, 25, 1] [1, 25, 3, 5, 7] [1, 25, 3, 5, 7]

B. [1, 25, 3, 5, 7] [5,1,3,7,25]

C. [1, 25, 3, 5, 7] [7, 5, 3, 25, 1] [7, 5, 3, 25, 1] [7, 5, 3, 25, 1]

D. An error is thrown

const arr1 = ['a', 'b', 'c'];
const arr2 = ['b', 'c', 'a'];

console.log(
  arr1.sort() === arr1,
  arr2.sort() == arr2,
  arr1.sort() === arr2.sort()
);

A. true true true

B. true true false

C. false false false

D. true false true

function ArrayBoolean() {
  if ([] == true && [1] == true) return [true, true];
  else if ([] == true && [1] == false) return [true, false];
  else if ([] == false && [1] == true) return [false, true];
  else return [false, false];
}
ArrayBoolean();

A. [true, true]

B. [true, false]

C. [false, true]

D. [false, false]

let dog = {
  breed: 'Border Collie',
  sound: 'Wooh',
  getBreed: () => {
    return this.breed;
  },
  getSound: function() {
    return this.sound;
  }
};
console.log(dog.getBreed(), dog.getSound());

A. Border Collie, Wooh

B. Border Collie, undefined

C. undefined, Wooh

D. undefined, undefined

const person = { name: 'duthaho' };

function sayHi(age) {
  return `${this.name} is ${age}`;
}

console.log(sayHi.call(person, 69));
console.log(sayHi.bind(person, 69));

A. undefined is 69 duthaho is 69

B. function function

C. duthaho is 69 duthaho is 69

D. duthaho is 69 function

function withVar() {
  const b = () => a;
  var a = 24;
  return b;
}

function withLet() {
  const b = () => a;
  let a = 24;
  return b;
}

function changingValue() {
  let a = 24;
  const b = () => a;
  a = 42;
  return b;
}

console.log(withVar()()); // ??
console.log(withLet()()); // ??
console.log(changingValue()()); // ??

A. undefined Error 42

B. 24 Error 24

C. 24 24 42

D. undefined Error 24

let a = new Date('2019,1,1').toLocaleDateString();
let b = new Date(2019, 1, 1).toLocaleDateString();
console.log(a, b);

A. 1/1/2019 2/1/2019

B. 1/1/2019 1/1/2019

console.log(fetch);

A. The fetch function

B. A reference error

C. It depends

const a = 0.1;
const b = 0.2;
const c = 0.3;

console.log(a + b === c);

A. True

B. False

function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
}

const ti = new Person('du', 'ti');
const teo = Person('du', 'teo');

console.log(ti);
console.log(teo);

A. Person {firstName: "du", lastName: "ti"} undefined

B. Person {firstName: "du", lastName: "ti"} Person {firstName: "du", lastName:"teo"}'

C. Person {firstName: "du", lastName: "ti"} {}

D. Person {firstName: "du", lastName: "ti"} ReferenceError

bar();

var bar;

function bar() {
	console.log('first');
}

bar = function () {
	console.log('second');
};

bar();

foo();

function foo() {
	console.log(1);
}

var foo = function () {
	console.log(2);
};

function foo() {
	console.log(3);
}

foo();

A. second first 1 3

B. first second 3 2

C. second first 3 3

D. first second 3 3

function sayHi() {
  return (() => 0)();
}

console.log(typeof sayHi());

A. object

B. number

C. function

D. undefined

const a = {
  stringField: 'Joe',
  numberField: 123,
  dateField: new Date('1995-12-17T03:24:00'),
  nestedField: { field: 'Nested' }
};

const b = JSON.parse(JSON.stringify(a));

console.log(
  a.stringField === b.stringField,
  a.numberField === b.numberField,
  a.dateField === b.dateField,
  a.nestedField.field === b.nestedField.field
);

A. true true true true

B. true true true false

C. true true false true

D. false false false false

const notifications = 1;

console.log(
  `You have ${notifications} notification${notifications !==
    1 && 's'}`
);

A. You have 1 notification

B. You have 1 notifications

C. You have 1 notificationfalse

const compare = a => a === a;

console.log(compare(null));
console.log(compare(undefined));
console.log(compare(NaN));
console.log(compare([NaN]));

A. true true true true

B. true false true true

C. true true false true

D. true true false false

const n = 5;

console.log(1..n); // ?

A. [1, 2, 3, 4, 5]

B. undefined

C. Syntax error

const a = {
  stringField: 'Joe',
  nestedField: { field: 'Nested' },
  functionField: () => 'aReturn'
};

const b = Object.assign({}, a);

b.stringField = 'Bob';
b.nestedField.field = 'Changed';
b.functionField = () => 'bReturn';

console.log(
  a.stringField,
  a.nestedField.field,
  a.functionField()
);

A. Joe Nested aReturn

B. Bob Changed bReturn

C. Joe Changed aReturn

D. Bob Nested bReturn

const url = 'quiz.duthaho.com';
const { length: ln, [ln - 1]: domain = 'quiz' } = url
  .split('.')
  .filter(Boolean);
console.log(domain);

A. "quiz"

B. "duthaho"

C. "com"

D. undefined

const obj = { a: 'one', b: 'two', a: 'three' };
console.log(obj);

A. {a: "one", b: "two" }

B. {b: "two", a: "three" }

C. {a: "three", b: "two" }

D. SyntaxError

const user = {
  name: 'lao Hac',
  age: 69,
  pet: {
    type: 'cho',
    name: 'vang'
  }
};

Object.freeze(user);

user.pet.name = 'shiba';

console.log(user.pet.name);

A. shiba

B. vang

C. An error is thrown

const obj = {
  1: 1,
  2: 2,
  3: 3
};

console.log(Object.keys(obj), Object.values(obj));

A. [1, 2, 3] ["1", "2", "3"]

B. ["1", "2", "3"] [1, 2, 3]

C. ["1", "2", "3"] ["1", "2", "3"]

const obj = { 1: 'a', 2: 'b', 3: 'c' };
const set = new Set([1, 2, 3, 4, 5]);

obj.hasOwnProperty('1');
obj.hasOwnProperty(1);
set.has('1');
set.has(1);

A. false true false true

B. false true true true

C. true true false true

D. true true true true

const a = {};
const b = { key: 'b' };
const c = { key: 'c' };

a[b] = 123;
a[c] = 456;

console.log(a[b]);

A. 123

B. 456

C. undefined

D. ReferenceError

const scrambled = {
  2: 'e',
  5: 'o',
  1: 'h',
  4: 'l',
  3: 'l'
};

const result = Object.values(scrambled).reduce(
  (agg, el) => agg + el,
  ''
);

console.log(result);

A. hello

B. eohll

C. Cả A, B đều đúng

D. Cả A, B đều sai

let b = '4';

console.log(b++ + 3, b);

A. 44 4

B. 8 5

C. 7 5

D. 43 5

console.log(1 < 2 < 3);
console.log(3 > 2 > 1);

A. true true

B. true false

C. false false

D. undefined undefined

A. HEAD, HTML, BODY

B. HEAD, TITLE, BODY

C. HEAD, BODY, HTML

D. HTML, HEAD, BODY

A. <HR>

B. <P>

C. <BR>

D. <PRE>

A. NAME

B. CLASS

C. HREF 

D.  ID

A. <PIC>

B.  <IMG>

C. <IMAGE>

D. <PICTURE>

A.  <ADDRESS>

B.  <PRE>

C. <BLOCKQUOTE> 

D. <AUTHOR>

A. <span>

B. <pre>

C. <blockquote>

D. <div>

A.  <li>

B. <ul> 

C. <lo>

D. <dl>

A. <color>

B.  <font>

C. <fontstyle>

D. <fontsize>

A. <tr>

B. <td>

C. <table>

D. <th>

A. <tr>

B. <td>

C. <table>

D. <th>

A. Colspan 

B. Align

C. Rowspan

D. Valign

A. Colspan

B. Align

C. Rowspan

D. Valign

A. <frame>

B. <noframe>

C.  <ifframe> 

D. <frameset>

A. <input type= “text”>

B. <input type = “hidden”

C. <input type= “password”

D. <textarea>

A.  <input type= “text”>

B. <input type = “hidden”

C. <input type= “password”

D. <textarea>

A.  <input type= “text”>

B. <input type = “radio”

C. <input type= “checkbox” 

D. <textarea>