Expand binary assignments

Option: transforms.expandBinaryAssignment

What it changes

Expands arithmetic and bitwise compound assignments into simple assignments while preserving single evaluation of member receivers and computed keys.

a += b;
a **= 2;
obj.x -= y;
arr[idx()] |= v;

a = a + b;
a = a ** 2;
(_obj = obj).x = _obj.x - y;
(_arr = arr)[_idx = idx()] = _arr[_idx] | v;

Run this transform by setting transforms.expandBinaryAssignment to true:

obfuscate.mjs

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

Open the TypeScript implementation on GitHub.

Review behavior checks and cases this transform leaves alone.

Last modified on August 26, 2026