How do I run CodePen files?

By default, every time you save your project runs and automatically updates the preview. You can save and run your project by clicking the “Save All + Run” button in the header . You can also use the keyboard shortcut to save your current file (Command + S for Mac, CTRL + S for PC).

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Why is ReactDOM undefined?

When you encounter an error saying ‘ReactDOM’ is not defined, it means that your application is can’t find the variable ReactDOM because it hasn’t been initialized yet . Generally, “X is not defined error” is caused by wrong import and different letter case between import and the imported variable call.16 Eki 2020

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Why is ReactDOM undefined?

When you encounter an error saying ‘ReactDOM’ is not defined, it means that your application is can’t find the variable ReactDOM because it hasn’t been initialized yet . Generally, “X is not defined error” is caused by wrong import and different letter case between import and the imported variable call.16 Eki 2020

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