Function declarations to expressions

Option: transforms.functionDeclarationToExpression

What it changes

Rewrites eligible function declarations in scripts and function bodies as var-initialized function expressions. Declarations stay unchanged when moving initialization to their statement position could alter execution.

Before and after

const TAX = 0.2;
function withTax(n) {
  return n + n * TAX;
}
total = withTax(100);

const TAX = 0.2;
var withTax = function (n) {
  return n + n * TAX;
};
total = withTax(100);

Configuration

Run this transform by setting transforms.functionDeclarationToExpression to true:

obfuscate.mjs

const output = obfuscate(source, {
  transforms: {
    functionDeclarationToExpression: true,
  },
})

View the implementation

Open the TypeScript implementation on GitHub.

Read the behavior tests

Review behavior checks and cases this transform leaves alone.

Last modified on August 26, 2026

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Reference

Support

Function declarations to expressions

What it changes

Before and after

Configuration

View the implementation

Read the behavior tests

​What it changes

​Before and after

​Configuration

View the implementation

Read the behavior tests

What it changes

Before and after

Configuration