JS-Exam

1.Given the following code:

document.body.addEventListener(‘ click ’, (event) => {

if (/* CODE REPLACEMENT HERE */) { console.log(‘button clicked!’); )

});

Which replacement for the conditional statement on line 02 allows a developer to correctly determine that a button on page is clicked?

• Event.clicked

• e.nodeTarget ==this

• event.target.nodeName == ‘BUTTON’

• button.addEventListener(‘click’)

function Tiger() {

this.Type = 'Cat';

this.size = 'large';

}

let tony = new Tiger();

tony.roar = () => { console.log('Theyre great1'); };

function Lion() {

this.type = 'Cat';

this.size = 'large';

}

17  //Insert code here

18// leo.roar();

Which two statements could be inserted at line 17 to enable the function call on line 18? Choose 2 answers.

• leo.roar = () => { console.log(‘They\’re pretty good:’); };

• Object.assign(leo,Tiger);

• Object.assign(leo,tony);

• Leo.prototype.roar = () => { console.log(‘They\’re pretty good:’); };

4. Consider type coercion, what does the following expression evaluate to?

True + 3 + ‘100’ + null

• 104

• 4100

• ‘3100null’

• ‘4100null’

// 5. Refer to the code below

const pi = 3.1415326;

// What is the data type of pi?

• Double

• Number

• Decimal

• Float

// 7. Which statement parses successfully?

• JSON. parse ('"foo"')

• JSON.parse (""foo'")

• JSON.parse ("foo");

• JSON.parse ("foo");

10. Given two expressions var1 and var2. What are two valid ways to return the logical AND of the two expressions and ensure it is data type Boolean? Choose 2 answers:

• Boolean(var1 && var2)

• var1 && var2

• var1.toBoolean() && var2toBoolean()

• Boolean(var1) && Boolean(var2)

11. A developer has an ErrorHandler module that contains multiple functions. What kind of export leverages so that multiple functions can be used?

• Named

• All

• Multi

• Default

// 15. Refer to the code snippet below:

let array = [1, 2, 3, 4, 4, 5, 4, 4];

for (let i =0; i < array.length; i++){

if (array[i] === 4) {

array.splice(i, 1);

}}

• [1, 2, 3, 4, 5, 4, 4]

• [1, 2, 3, 4, 4, 5, 4]

• [1, 2, 3, 4, 5, 4]

• [1, 2, 3, 5]

16. Refer to the code below: let str = ‘javascript’; str[0] = ‘J’; str[4] = ’S’;

After changing the string index values, the value of str is ‘javascript’.

What is the reason for this value:

• Non-primitive values are mutable.

• Non-primitive values are immutable.

• Primitive values are mutable.

• Primitive values are immutable.

18. The developer wants to test the array shown:

const arr = Array(5).fill(0)

Which two tests are the most accurate for this array? Choose 2 answers:

• console.assert( arr.length === 5 );

• arr.forEach(elem => console.assert(elem === 0))

• console.assert(arr[0] === 0 && arr[ arr.length] === 0);

• console.assert (arr.length >0);