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Detects ES5 polyfills and legacy JavaScript code
Rule IDperf/legacy-js
CategoryPerformance
ScopePer-page
Severityinfo
Weight3/10

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Solution

Consider removing legacy polyfills if you don’t need to support old browsers. Use differential serving (module/nomodule) to send modern code to modern browsers. Update Babel/TypeScript target to ES2020+ if your audience uses modern browsers. Check browserslist configuration.

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Enable / Disable

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Disable this rule

squirrel.toml
[rules]
disable = ["perf/legacy-js"]

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Disable all Performance rules

squirrel.toml
[rules]
disable = ["perf/*"]

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Enable only this rule

squirrel.toml
[rules]
enable = ["perf/legacy-js"]
disable = ["*"]