JavaScript for QA Automation

MODULE 1 OF 10 • THEORY

1. Variables & Scope (let, const)

basic

Use "const" for values that should not change after assignment (like timeouts, URLs, and element selectors). Use "let" for values that will be reassigned (like loop counters, toggle states, and retry accumulators). Avoid "var" because it is function-scoped and can cause leakages.

Syntax Template

const TIMEOUT = 5000;
let retryCount = 0;

When to use

Always prefer const by default. Only use let when you explicitly plan to change the variable's value later in the test execution.

Best practice

Declare selectors and configuration objects with "const" to prevent accidental runtime reassignments that would break E2E test runs.

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v18.16.0

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