react/packages/react-dom/npm/index.js

'use strict';

function checkDCE() {
  /* global __REACT_DEVTOOLS_GLOBAL_HOOK__ */
  if (
    typeof __REACT_DEVTOOLS_GLOBAL_HOOK__ === 'undefined' ||
    typeof __REACT_DEVTOOLS_GLOBAL_HOOK__.checkDCE !== 'function'
  ) {
    return;
  }
  if (process.env.NODE_ENV !== 'production') {
    // This branch is unreachable because this function is only called
    // in production, but the condition is true only in development.
    // Therefore if the branch is still here, dead code elimination wasn't
    // properly applied.
    // Don't change the message. React DevTools relies on it. Also make sure
    // this message doesn't occur elsewhere in this function, or it will cause
    // a false positive.
    throw new Error('^_^');
  }
  try {
    // Verify that the code above has been dead code eliminated (DCE'd).
    __REACT_DEVTOOLS_GLOBAL_HOOK__.checkDCE(checkDCE);
  } catch (err) {
    // DevTools shouldn't crash React, no matter what.
    // We should still report in case we break this code.
    console.error(err);
  }
}

if (process.env.NODE_ENV === 'production') {
  // DCE check should happen before ReactDOM bundle executes so that
  // DevTools can report bad minification during injection.
  checkDCE();
  module.exports = require('./cjs/react-dom.production.min.js');
} else {
  module.exports = require('./cjs/react-dom.development.js');
}