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@babel/helper-annotate-as-pure

JavaScript
declare export default annotateAsPure(nodeOrPath: Node | NodePath);

Usage​

JavaScript
import traverse from "@babel/traverse";
import annotateAsPure from "@babel/helper-annotate-as-pure";

// ...

traverse(file, {
  CallExpression(path) {
    annotateAsPure(path);
  },
});

Caveat with UglifyJS pre v3.1.0​

@babel/helper-annotate-as-pure will append any existing leading comments to the #__PURE__ annotation. Versions of UglifyJS prior to v3.1.0 will ignore these annotations, as they only check the last leading comment for the annotation.

For example, using the Usage snippet above:

In

JavaScript
const four = /* foo */ add(2, 2);

Out

JavaScript
const four = /* #__PURE__ */ /* foo */ add(2, 2);