Free JavaScript-Developer-I: Salesforce Certified JavaScript Developer I Exam Questions and Answers

Last updated: September 19, 2026

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1. Question #1

   A developer receives a comment from the Tech Lead that the code given below has error: const monthName = ‘July’; const year = 2019; if(year === 2019) { monthName = ‘June’; } Which line edit should be made to make this code run?

   • A. 01 let monthName =’July’;
   • B. 02 let year =2019;
   • C. 02 const year = 2020;
   • D. 03 if (year == 2019) {
   Reveal Answer

2. Question #2

   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:

   • A. Non-primitive values are mutable.
   • B. Non-primitive values are immutable.
   • C. Primitive values are mutable.
   • D. Primitive values are immutable.
   Reveal Answer

3. Question #3

   A developer has the following array of student test grades: Let arr = [ 7, 8, 5, 8, 9 ]; The Teacher wants to double each score and then see an array of the students who scored more than 15 points. How should thedeveloper implement the request?

   • A. Let arr1 = arr.filter(( val) => ( return val > 15 )) .map (( num) => ( return num *2 ))
   • B. Let arr1 = arr.mapBy (( num) => ( return num *2 )) .filterBy (( val ) => return val > 15 )) ;
   • C. Let arr1 = arr.map((num) => num*2). Filter (( val) => val > 15);
   • D. Let arr1 = arr.map((num) => ( num *2)).filterBy((val) => ( val >15 ));
   Reveal Answer

4. Question #4

   A developer is creating a simple webpage with a button. When a userclicks this button for the first time, a message is displayed. The developer wrote the JavaScript code below, but something is missing. The message gets displayed every time a user clicks the button, instead of just the first time. Which two code lines make this code work as required? Choose 2 answers

   

   Select 2 answers.

   • A. On line 02, use event.first to test if it is the first execution.
   • B. On line 04, useevent.stopPropagation ( ),
   • C. On line 04, use button.removeEventListener(‘ click” , listen);
   • D. On line 06, add an option called once to button.addEventListener().
   Reveal Answer

5. Question #5

   Refer to the code below: const event = new CustomEvent( //Missing Code ); obj.dispatchEvent(event); A developer needs to dispatch a custom event called update to send information about recordId. Which two options could a developer insert at the placeholder in line 02 to achieve this? Choose 2 answers

   Select 2 answers.

   • A. ‘Update’ , ( recordId : ‘123abc’ (
   • B. ‘Update’ , ‘123abc’
   • C. { type : ‘update’, recordId : ‘123abc’ }
   • D. ‘Update’ , { Details : { recordId : ‘123abc’}}
   Reveal Answer

6. Question #6

   Refer to the code below: Let car1 = new Promise((_ , reject) => setTimeout(reject, 2000, “car 1 crashed in” => Let car2 =new Promise(resolve => setTimeout(resolve, 1500, “car 2 completed”) Let car3 =new Promise(resolve => setTimeout(resolve, 3000, “car 3 completed”) Promise.race(( car1, car2, car3)) .t hen (value => ( Let result = ‘$(value) the race.’;)} .catch(arr => { console.log(“Race is cancelled.”, err); }); What isthe value of result when Promise.race executes?

   • A. Car 3 completes the race
   • B. Car 2 completed the race.
   • C. Car 1 crashed in the race.
   • D. Race is cancelled.
   Reveal Answer

7. Question #7

   Given the code below: Function myFunction(){ A =5; Var b =1; } myFunction(); console.log(a); console.log(b); What is the expected output?

   • A. Both lines 08 and 09 are executed, and the variables are outputted.
   • B. Line 08outputs the variable, but line 09 throws an error.
   • C. Line 08 thrones an error, therefore line 09 is never executed.
   • D. Both lines 08 and 09 are executed, but values outputted are undefined.
   Reveal Answer

8. Question #8

   Refer to HTML below: <div id =”main”> <div id = “ card-00”>This card is smaller.</div> <div id = “card-01”>The width and height of this card is determined by its contents.</div> </div> Which expression outputs the screen width of the element with the ID card-01?

   • A. document.getElementById(‘ card-01 ’).getBoundingClientRest().width
   • B. document.getElementById(‘ card-01 ’).style.width
   • C. document.getElementById(‘ card-01 ’).width
   • D. document.getElementById(‘ card-01 ’).innerHTML.lenght*e
   Reveal Answer

9. Question #9

   Given the following code: is the output of line 02?

   
   • A. ''x''
   • B. ''null'''
   • C. ''object''
   • D. ''undefined''
   Reveal Answer

10. Question #10

    A developer writers the code below to calculate the factorial of a given number. What isthe result of executing line 04?

    
    • A. 6
    • B. -Infinity
    • C. RuntimeError
    Reveal Answer