Node js filter array with reactive form values

Question

I've got probelm with filtering array from form values.

I using angular 7 and express js

export function getItems(req: Request, res: Response) {
  const itemCriteria: ItemCriteria = req.body.itemCriteria;
  const name = (itemCriteria.name) ? itemCriteria.name : '';
  const description= (itemCriteria.description) ? 
itemCriteria.description: '';
  const category= itemCriteria.category;

  const filterItems: Item[] = items
    .filter(item=> item.category.id === category &&
               item.name .includes(name ) &&
               item.description.includes(description)
    );

  res.status(200).json(filterItems);
}

When I fill all fields filterItems is correct, but when I fill only one or two fields I've got error 'Cannot read property of undefinied'. This fields is from reactive form but only one is required else is optional. So my question is how can I filter this array correct?

Error is in backend my fake node js server. This values: name, description, category is from frontend (reactive forms values) — Bartas
– Bartas, Commented Jun 23, 2019 at 18:47

Julian W. · Accepted Answer · 2019-06-23 18:56:10Z

1

When one of Criteria is empty, you don't have to include it in the filter function.

So you can change it by following.

const filterItems: Item[] = items
  .filter(item=> (!category || (item.category && item.category.id === category)) &&
    (!name || (item.name && item.name.includes(name))) &&
    (!description || (item.description && item.description.includes(description))
  );

answered Jun 23, 2019 at 18:56

Julian W.

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Comments

pteranobyte · Accepted Answer · 2019-06-23 18:23:55Z

0

You are trying to read a property of an undefined variable. It's hard to know which one it is, but you can protect your code from these types of errors by making sure a variable is defined like this:

const myProperty = someVariable && someVariable.someProperty

This shortcircuits if someVariable is falsy.

In your case this might look like:

const filterItems: Item[] = items
    .filter(item=> item && item.category && item.category.id === category &&
               item.name && item.name.includes(firstName) &&
               item.description && item.description.includes(lastName)
    );

(also it's not clear where firstName, lastName, and items come from, but I don't think that's the cause of the error you're asking about)

answered Jun 23, 2019 at 18:23

pteranobyte

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1 Comment

Bartas Over a year ago

Yeah, my bad when I wrote post here whith variables. Your solution is good because I don't have error but filters array is no correct :/ I think the problem is I filter values but few might be empty for example: Form: category is 1, name is 'Item1' description is empty. So statement whith description is not met

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