The answer is that the On Load client script runs before the GlideAjax response is received, leaving the cost center field empty. This happens because GlideAjax performs an asynchronous call to the server, meaning the script continues executing immediately without pausing for the server’s reply. The callback function that updates the field only fires after the response arrives, which is too late for the initial form load. On the ServiceNow Certified Application Developer CAD exam, this scenario tests your understanding of client-side timing and the asynchronous nature of GlideAjax, often appearing as a trap where candidates assume synchronous behavior. A common memory tip is to think of GlideAjax as sending a letter—you don’t stand at the mailbox waiting for a reply; you go about your day and check later. For On Load scripts, the form finishes loading before the “letter” returns, so any field updates from the callback won’t appear until after the load event completes.
SNOW-CAD Core Application Development Practice Question
This SNOW-CAD practice question tests your understanding of core application development. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A junior developer is creating a new catalog item for requesting software licenses. The catalog item includes several variables such as software name, quantity, and cost center. The business requires that when a user submits the request, the cost center variable should automatically populate with the cost center of the user's manager. The developer has written a script in the 'On Load' catalog client script to populate the cost center field. However, during testing, the cost center field remains empty after the form loads. The developer checks the script and finds it uses GlideAjax to call a Scripted REST API to fetch the manager's cost center. What is the most likely cause of the issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The 'On Load' client script runs before the GlideAjax response is received.
The 'On Load' catalog client script triggers when the form loads, but GlideAjax makes an asynchronous call to the server. The script continues executing without waiting for the response, so the cost center variable remains empty until the callback fires. Since the callback updates the field asynchronously, the field appears empty on load because the response hasn't arrived yet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The cost center variable is read-only and cannot be set by client scripts.
Why it's wrong here
Incorrect: If read-only, it wouldn't be empty; it would ignore the set, but likely not the issue.
✗
The Scripted REST API is not accessible from client scripts due to cross-origin restrictions.
Why it's wrong here
Incorrect: GlideAjax works within ServiceNow without CORS issues.
✗
The GlideAjax call is missing the callback function.
Why it's wrong here
Plausible but not most likely; the callback could exist but still timing issue.
✓
The 'On Load' client script runs before the GlideAjax response is received.
Why this is correct
Correct: The script sets the field value before the async response returns.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
ServiceNow often tests the asynchronous nature of GlideAjax in client scripts, tricking candidates into thinking the issue is a missing callback or a permission problem, when the real flaw is the timing of the response relative to the form load.
Detailed technical explanation
How to think about this question
GlideAjax in ServiceNow sends an XMLHttpRequest asynchronously by default. The 'On Load' client script runs synchronously with the form rendering, but the AJAX response is handled later by the callback function. This is a classic race condition: the form finishes loading before the server responds, leaving the field empty until the callback eventually sets it. To fix this, developers often use synchronous GlideAjax (async: false) or move the logic to a 'On Change' or 'On Submit' client script.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the SNOW-CAD exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Core Application Development — This question tests Core Application Development — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The 'On Load' client script runs before the GlideAjax response is received. — The 'On Load' catalog client script triggers when the form loads, but GlideAjax makes an asynchronous call to the server. The script continues executing without waiting for the response, so the cost center variable remains empty until the callback fires. Since the callback updates the field asynchronously, the field appears empty on load because the response hasn't arrived yet.
What should I do if I get this SNOW-CAD question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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