parse my json to get values - json sent from Xcode to JS front-end

Question

Trying to parse and read my JSON data.
I am passing my json data from Xcode to my React native front-end.
I have tried JSON.parse and JSON.stringify nothing works.
It always logs "NULL". I need to access the "value" Help please!!

JSON in Xcode

{
  "myDictionary" : {
    "BG" : [
      "{\"value\":\"8 mg\\\/dL\",\"endDate\":635390040,\"startDate\":635390040,\"type\":\"bloodGlucose\"}",
      "{\"value\":\"6 mg\\\/dL\",\"endDate\":635393640,\"startDate\":635393640,\"type\":\"bloodGlucose\"}"
    ]
  }
}

JS:

const log = HealthkitController.getBloodGlucose()
    .then(result => {
     let res = JSON.parse(result)
      for (let i = 0; i < res.length; i++) {
        let final = res[0];        
        console.log(final)         // prints the first object
        let fin = final["value"]
        console.log(fin)           //undefined (doesn't print 8mg/dL)
 }
})

result:

["{\"value\":\"8 mg\\\/dL\",\"endDate\":635390040,\"startDate\":635390040,\"type\":\"bloodGlucose\"}",
"{\"value\":\"6 mg\\\/dL\",\"endDate\":635393640,\"startDate\":635393640,\"type\":\"bloodGlucose\"}"]

Please confirm if 'result' is getting the stringified response then only JSON.parse will work. As of now, only BG node contains the stringified objects as elements. — Diwakar Singh
– Diwakar Singh, Commented Feb 19, 2021 at 9:28
@DiwakarSingh check question. I added result. I want to access the value. — grooot
– grooot, Commented Feb 19, 2021 at 9:49

Dan · Accepted Answer · 2021-02-19 11:49:47Z

0

Your result is coming back as an Array of strings. If you want to extract the value you can do something like this

const values = results.map(result => {
 const { value } = JSON.parse(result);
 return value;
});

The output will be:

["8 mg/dL", "6 mg/dL"]

answered Feb 19, 2021 at 11:49

Dan

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Comments

ru4ert · Accepted Answer · 2021-02-19 10:17:39Z

0

What does this create?

const log = HealthkitController.getBloodGlucose()
.then(result => {
        for (var i = 0; i < result.lenght; i++{
                let res = JSON.parse(result[i])
                console.log(res) //always null
            }
        });

edited Feb 19, 2021 at 10:17

answered Feb 19, 2021 at 9:27

ru4ert

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3 Comments

grooot Over a year ago

"result" contains my JSON (check updated question). I want to access the value.

grooot Over a year ago

check my updated code. it prints "undefined"

ru4ert Over a year ago

yes, because you have walk through the array. Wait 2 minutes, I will fix this.

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