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JavaScript Using SQL ORMs with Node.js Defining Models Handle Validation Errors

Posted by Lewis Sheeran
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Lewis Sheeran
Web Development Techdegree Graduate 19,398 Points

Confused about the mapping method being used here

const errors = error.errors.map(err => err.message)

In the code above, can someone please explain to me what part .errors plays in this line?

is .errors a property of the error object?

Why wouldn't the line be const errors = error.map(err => err.message) instead?

2 Answers

Jason Larson
Jason Larson
8,361 Points

I will start by saying that I don't really know all that much about error. Having said that, I can also say that I know enough about JavaScript that I can probably still answer your question. Yes, errors is a property of error. The fact that you are using a .map() method on it means that it is an array. You can't do const errors = error.map(err => err.message) because error is an object, and .map() only works on arrays.

Lewis Sheeran
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Lewis Sheeran
Web Development Techdegree Graduate 19,398 Points

Thanks Jason. I get it now.

Shawn Calhoun
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Shawn Calhoun
Full Stack JavaScript Techdegree Graduate 16,644 Points
Shawn Calhoun
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Shawn Calhoun
Full Stack JavaScript Techdegree Graduate 16,644 Points

Just to add to Jason's point I've added this from the lesson:

The error thrown by Sequelize contains an errors property, which is an array with 1 or more ValidationErrorItems, each represents a failed validation. Before displaying the error, we want to check the type of error.