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plugin-transform-react-jsx sets null on attributes parameter, but should be undefined. #9130

jklarenbeek opened this Issue Dec 5, 2018 · 1 comment


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jklarenbeek commented Dec 5, 2018

Bug Report

Current Behavior
When JSX is transformed and encounters a element without attributes:

const jsx = (<h1>test</h1>);

the h (or React.createElement) function is called with an attributes parameter of null instead of undefined. Therefor the default value for a parameter does not kick in.

Input Code

Note the top function signature of h with a default value of an empty object literal for the attributes parameter.

function h(name, attributes = {}, {

Expected behavior/code
I expect the attributes parameter to be undefined or defaulting to an empty object, if the default value for a parameter is set. Null in this case is not an option and only adds to the internal logic of the jsx render function.

Babel Configuration (.babelrc, package.json, cli command)

  "babel": {
    "presets": [
          "modules": false,
          "useBuiltIns": false,
          "debug": true
    "plugins": [
          "pragma": "h"


  • Babel version(s): ^7.1.5
  • Node/npm version: 10.12.0
  • OS: windows 10
  • plugin-transform-react-jsx version: ^7.0.0

Possible Solution
I can work around it ofcourse, but it doesn't use the buildin default value operator for parameters into account that was defined for javascript.


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babel-bot commented Dec 5, 2018

Hey @jklarenbeek! We really appreciate you taking the time to report an issue. The collaborators
on this project attempt to help as many people as possible, but we're a limited number of volunteers,
so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack
community that typically always has someone willing to help. You can sign-up here
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