When I first started learning, I only learned things necessary for employment, so I didn't really understand the basics, but it's good to go after setting the basics right. I wonder if the code sandbox has been updated in the meantime. let escapingString = 'bad \'string\' will tell you.'; // When writing this code, if you set the variable with quotation marks and save it, it automatically changes to double quotation marks, and the part with backslashes inside the quotation marks is automatically deleted. I think the function has been optimized. I highly recommend it as a class to set the basics right.