looping through an json array list

Question

the following array list I need to get all the price one by one. this returns the full json object console.log('File data:', jsonString); but the for loop never seems to get called , it never enters it. I need to loop through a json file but its in different folder the json file is under menu folder called list.json menu-> projectName\menu\list.json the file looks like this The data:

[
  {
    "code": "ZC",
    "price": "1"
  },
  {
    "code": "ZS",
    "price": "3"
  },
  {
    "code": "VC",
    "price": "4"
  },
...]

JS:

const jsonList = fs.readFile("../menu/list.json", "utf8", (err, jsonString) => {
  if (err) {
    console.log("File read failed:", err);
    return;
  }
  console.log("File data:", jsonString);
  console.log("File data:", jsonString.url);
  for (var key in jsonString) {
    if (jsonString.hasOwnProperty(key)) {
      console.log("===>", jsonString[key].price);
    }
    return jsonString;
  }
});

I think you need to convert your jsonList using JSON.parse method something like jsonList = JSON.parse(jsonList) just before your for loop — Syam
– Syam, Commented May 5, 2020 at 5:29
Not sure of the issue with your code but a simpler approach might be jsonList.forEach { item => console.log("==>" + item.price } — Chris
– Chris, Commented May 5, 2020 at 5:32

ROOT · Accepted Answer · 2020-05-05 06:21:43Z

1

There are two ways to fix the issue you are facing, one is to have your code run inside the callback:

const jsonList = fs.readFile("../menu/list.json", "utf8", (err, jsonString) => {
  if (err) {
    console.log("File read failed:", err);
    return;
  }
  console.log("File data:", jsonString);
  for (var key in JSON.parse(jsonString)) {
    if (jsonList.hasOwnProperty(key)) {
      console.log("===>", jsonList[key].price); // This is never called
    }
  }
});

or by using sync function to read file:

const jsonString = fs.readFileSync("../menu/list.json", "utf8");
console.log("File data:", jsonString);
const jsonList = JSON.parse(jsonString);
for (var key in jsonList) {
  if (jsonList.hasOwnProperty(key)) {
    console.log("===>", jsonList[key].price); // This is never called
  }
}

edited May 5, 2020 at 6:21

answered May 5, 2020 at 5:56

ROOT

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7 Comments

benji_r Over a year ago

the sync function returns undefined, I dont get it

benji_r Over a year ago

console.log("File data:", jsonString); this returns the json object but the .price is undefined :(

benji_r Over a year ago

both are undefined

ROOT Over a year ago

@benji_r, can you post the file list.json structure?

benji_r Over a year ago

that was it thank you so much const jsonList = JSON.parse(jsonString);

|

Chris · Accepted Answer · 2020-05-05 05:36:45Z

1

I think you need to loop in the callback as it is async and so jsonList is not the object you expect when you access it. See Get data from fs.readFile

answered May 5, 2020 at 5:36

Chris

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9 Comments

benji_r Over a year ago

this is giving me undefiend console.log('====> ', jsonList);

Chris Over a year ago

I think that makes sense based on async - what if you put console.log(jsonString) instead of return jsonString. Does that show it as you expect at that point

benji_r Over a year ago

console.log('File data:', jsonString); this gives me the correct stuff, however moving the forloop into the fs .readfile returns undefined

benji_r Over a year ago

for (var key in jsonString) { console.log('byeeeee') if (jsonString.hasOwnProperty(key)) { console.log('===>',jsonString[key].price); } }

Chris Over a year ago

Possibly doesn't explain undefined but as Syam mentioned you need JSON.parse(jsonString) so instead of return jsonString, JSON.parse(jsonString).forEach { item => console.log(item.price) }

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