TypeError: Cannot assign to read only property 'length'

[simaQ]

Chrome Version: 47.0.2526.106 (64-bit)

throw this error.

Caused by Assertion.prototype.length method.

[chrisbwall]

+1: having the same issue any time I pass anything that isn't a strict primitive to expect()

[zwhitchcox]

+1 same

[larsgw]

+1: Same issue, but for all assertions

[larsgw]

Seems to be caused by 'use strict'.

---

A possible workaround for Babel/Babelify usage is including expect.js on its own, without Babel or Babelify parsing, as that adds a 'use strict'. This can be done, in the case of Babelify, by making a separate bundle without babelify specifically for expect.js, and then including both in your page:

browserify()
  .require('expect.js')
  .bundle()
  .pipe(fs.createWriteStream(path.join(__dirname, '../build/expect.js')))

browserify()
  .exclude(['expect.js'])
  .add('./test/*.js')
  .transform(babelify)
  .bundle()
  .pipe(fs.createWriteStream(path.join(__dirname, '../build/test.js')))

I can't get the Babelify ignore option to work (see babel/babelify#265), but that is probably a good option too.