Review JavaScript variable declarations, report every use of var with line numbers, and replace declarations with const or let according to reassignment. Explain variable scope and initialization behavior, and check affected browser execution paths.
Use when reviewing scripts, client components, bundles, or runtime behavior related to Prefer const and let over var. Inspect both source code and the browser execution path so fixes target the real bottleneck or bug.
Review the instructions the agent will receive before you install.
var's function scope and hoisting behavior regularly causes bugs where variables are accessible outside the block they were declared in. const and let enforce block scope and make code intent clearer — const signals that a binding should not be reassigned, which helps readers understand data flow.
Scan this JavaScript file for any use of var and flag every occurrence with line numbers.
Replace all var declarations with const or let as appropriate. Use const when the variable is never reassigned, let otherwise.
Explain why const and let are preferred over var, covering scope, hoisting, and temporal dead zone.
Review scripts, client components, and browser execution paths related to Prefer const and let over var. Flag exact imports, event handlers, runtime side effects, or blocking operations that violate the rule, and state how the change should be verified in the browser.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/javascript/const-let
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