cannot read property 'value' of undefined code example

Example 1: TypeError: Cannot read property 'createElement' of undefined

TypeError: Cannot read property 'createElement' of undefined
Originally had:
import { React, Fragment } from 'react';

To solve, instead use:
import React, { Fragment } from 'react';

Example 2: Cannot read property 'valueChanges' of undefined

this.yourFormGroup.get('controlName').valueChanges.subscribe(() => {
	//Executed code when is detected a change on the 'controlName'
});