SALESFORCE-PD1 User Interface Practice Question
A developer is working with a Lightning Web Component and needs to ensure reactive updates occur when an object property or array element changes inside a tracked property. What is the correct approach in modern LWC?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reassign the property reference (e.g., this.myObj = {...this.myObj}).
Assigning a new object or array reference (mutation via replacement) triggers reactivity in LWC tracked properties.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Reassign the property reference (e.g., this.myObj = {...this.myObj}).
Why this is correct
Assignment triggers reactivity by changing reference.
- ✗
Use @track on every inner property.
Why it's wrong here
@track is applied at the top-level property and primitive tracking is automatic.
- ✗
Call component.forceUpdate().
Why it's wrong here
Method does not exist.
- ✗
Mutate the nested property directly; LWC automatically deep-tracks all mutations.
Why it's wrong here
LWC shallow tracks objects/arrays; nested mutations require reassignment.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Salesforce exam blueprint
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