Reading dynamic array from Firebase

Question

I have a project in ionic3 in which I have Firebase Array as follows.

List = {User3: true, User8: true, User9: false}

The parameter names are not fixed and can change. So when I receive the array in the above format, I need to list out only the users which are true. I need an array as follows.

User = {User3, User8,}

Fow do I list out the parameter names in a for loop.

for(let item of List){
//I need to write item.User3 in order to retrive the value. But parameter name User3 is not fixed.
}

score 1 · Accepted Answer · 2017-09-11 16:04:07Z

1

Your List is not an "array". It's an object. It does not have "parameter names". It has properties. To get the properties (users) with a value of true, filter the object's properties, which you can obtain with Object.keys, for ones with a value of true. You could do this with something like

Object.keys(List).filter(user => List[user])

You cannot use for...of. That's for arrays, not objects.

You could also query just those nodes with a value of true, which can you find out how to do by consulting the Firebase documentation.

Minor point, but capitalizing variable names is confusing and non-standard. Normally capitalized identifiers are used for classes etc.

edited Sep 11, 2017 at 16:04

answered Sep 5, 2017 at 20:14

user663031

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2 Comments

Tapas Mukherjee Over a year ago

Thanks a lot for the solution.

sebaferreras Over a year ago

Please consider upvoting the answers if they helped you @TapasMukherjee. Otherwise other SO users may seem that the answer is just a workaround and it's not actually a good way to solve the OP.

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