Is there a more beautiful way to catch errors on a block of JSON Arrays?

Question

I have a bunch of data in a JSON that I need to parse, but some of them does not exist.

Hence, I currently, have the following try/catch(e) but is there a more elegant way to do so?

for (var u = 0; u < 100; u++) {
      try {
        var reactions = JSON.parse(dataParsed.data[u].reactions.summary.total_count)
      } catch (err) {
        console.log(err)
        var reactions = 0
      }
      try {
        var comments = JSON.parse(dataParsed.data[u].comments.summary.total_count)
      } catch (err) {
        var comments = 0
      }
      try {
        var shares = JSON.parse(dataParsed.data[u].shares.count);
      } catch (err) {
        var shares = 0
      }

      postArray.push({
        "id": dataParsed.data[u].id,
        "message": dataParsed.data[u].message,
        "createdTime": dataParsed.data[u].created_time,
        "fullPicture": dataParsed.data[u].full_picture,
        "reactions": reactions,
        "comments": comments,
        "shares": shares
      })
}

is `dataParsed` already parsed (like the name suggests), or not? If it is, why do `JSON.parse` again? If it is not, shouldn't you parse only the first part -- the JSON string at the top level (i.e. `JSON.parse(dataParsed).data[u].comments.summary.total_count`)? — Thilo, Jul 07 '19 at 03:11
Show us what `dataParsed` looks like for better answers. In particular, if it is already an object, or still a String. — Thilo, Jul 07 '19 at 03:16

Code Maniac · Answer 1 · 2019-07-07T03:26:51.750

3

You can use && (short circuiting ) and || (default vlaue)

var reactions = dataParsed && dataParsed.data[u] &&  dataParsed.data[u].reactions && dataParsed.data[u].reactions.summary && dataParsed.data[u].reactions.summary.total_count || 0

There's a proposal for optional chaining and Nullish Coalescing

var reactions = dataParsed?.data[u]?.reactions?.summary?.total_count ?? 0

edited Jul 07 '19 at 03:26

answered Jul 07 '19 at 03:09

Code Maniac

37,143
5
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60

Given that the OP was `var reactions = JSON.parse(...)` it might be better if the default value is valid JSON, otherwise you're just changing one error for another. ;-) – RobG Jul 07 '19 at 04:21

Jack Bashford · Answer 2 · 2019-07-07T03:18:34.643

1

Make a function:

function safeParse(propStr) {
  let r = 0;
  try {
    r = propStr.split(/\.|\[|\]/g).reduce((a, c) => a[c], {});
  } catch(e) {}
  return r;
}

var reactions = safeParse("dataParsed.data[u].reactions.summary.total_count");
var comments = safeParse("dataParsed.data[u].comments.summary.total_count");
var shares = safeParse("dataParsed.data[u].shares.count");

edited Jul 07 '19 at 03:18

answered Jul 07 '19 at 03:10

Jack Bashford

43,180
11
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score 0 · Answer 3 · answered Jul 07 '19 at 03:15

0

Just use value|0 to catch the value via binary operation. If value exists, then it will return value if not, then it will return 0

answered Jul 07 '19 at 03:15

Veggiebob

11
2

Unless *value* happens to be a useful falsey value, like `null` or `false`. ;-) – RobG Jul 07 '19 at 04:19
oh yeah that's a good point. In that case, such a short solution probably isn't possible :/ – Veggiebob Jul 07 '19 at 05:08

Is there a more beautiful way to catch errors on a block of JSON Arrays?

3 Answers3