CODEWITHSUNDEEP
javascriptjsonreact-nativecachingserialization
TIMEX
TIMEX

Reputation: 272134

How can I store/retrieve a JSON object that contains a function to fetch fresh data?

const Data = {
    teachers: {
        size: 15,
        num: 4,
        color: 'blue'
    }
}

const person = {
    name: 'John',
    group: Data.teachers, // This is Default. If I do this, the entire teachers tree gets cached. Later, teachers tree changes, this is unusable.
    group: () => Data.teachers // I want to do this, so that it fetches fresh data. But, see below for the LJSON problem...
}

I understand that JSON.stringify does not support functions.

I've looked into LJSON (https://github.com/MaiaVictor/LJSON). LJSON does not fix the problem. They also cache Data.teachers, as is. When using LJSON, if Data.teachers changes, then calling group() will not get the latest. It will return the old tree.

(Current stack is React-Native, with AsyncStorage, using JSON.stringify/parse.)

Upvotes: 0

Views: 127

Answers (1)

muka.gergely
muka.gergely

Reputation: 8329

Have you tried the toString() method of a Function & eval?

const fn = (arg) => {
  console.log('function:', arg)
}
fn('yes, it works')

const jsonFn = JSON.stringify(fn.toString()) // now its a JSON.stringified string
const newJsonFn = JSON.parse(jsonFn) // parsing it back from JSON to string
const newFn = eval(newJsonFn) // eval!!!
newFn('yes, it works again')

IMPORTANT

Yes, this snippet solves your problem. But don't forget that eval is a dangerous tool: about eval security issues.

Upvotes: 1

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