JavaScript-Developer-I Practice Test

Refer to code below:
Function muFunction(reassign){
Let x = 1;
var y = 1;
if( reassign ) {
Let x= 2;
Var y = 2;
console.log(x);
console.log(y);}
console.log(x);
console.log(y);}
What is displayed when myFunction(true) is called?

A. 2 2 1 1

B. 2 2 undefined undefined

C. 2 2 1 2

D. 2 2 2 2

Universal Container(UC) just launched a new landing page, but users complain that the website is slow. A developer found some functions that cause this problem. To verify this, the developer decides to do everything and log the time each of these three suspicious functions consumes.
console.time(‘Performance’);
maybeAHeavyFunction();
thisCouldTakeTooLong();
orMaybeThisOne();
console.endTime(‘Performance’);
Which function can the developer use to obtain the time spent by every one of the three functions?

A. console.timeLog()

B. console.getTime()

C. console.trace()

D. console.timeStamp()

Refer to the code below:
01 let car1 = new promise((_, reject) =>
02 setTimeout(reject, 2000, “Car 1 crashed in”));
03 let car2 = new Promise(resolve => setTimeout(resolve, 1500, “Car 2
completed”));
04 let car3 = new Promise(resolve => setTimeout (resolve, 3000, “Car 3
Completed”));
05 Promise.race([car1, car2, car3])
06 .then(value => (
07 let result = $(value) the race. `;
08 ))
09 .catch( arr => (
10 console.log(“Race is cancelled.”, err);
11 ));
What is the value of result when Promise.race executes?

A. Car 3 completed the race.

B. Car 1 crashed in the race.

C. Car 2 completed the race.

D. Race is cancelled.

is below:

< img src=”” height=”200” alt=”Image Preview…”/>
The JavaScript portion is:

01 functionpreviewFile(){
02 const preview = document.querySelector(‘img’);
03 const file = document.querySelector(‘input[type=file]’).files[0];
04 //line 4 code
05 reader.addEventListener(“load”, () => {
06 preview.src = reader.result;
07 },false);
08 //line 8 code
09 }
In lines 04 and 08, which code allows the user to select an image from their local computer , and to display the image in the browser?

A. 04 const reader = new File(); 08 if (file) URL.createObjectURL(file);

B. 04 const reader = new FileReader(); 08 if (file) URL.createObjectURL(file);

C. 04 const reader = new File(); 08 if (file) reader.readAsDataURL(file);

GIven a value, which three options can a developer use to detect if the value is NaN?
Choose 3 answers !

A. value == NaN

B. Object.is(value, NaN)

C. value === Number.NaN

D. value ! == value

E. Number.isNaN(value)