如果字段返回 TypeError，则忽略 JSON 解析错误

Question

This feels like a totally straightforward try/catch issue, but as a total javascript noob I am clearly missing something.

I am trying to parse data from the Cleveland Museum of Art open collections API. Everything works fine, except that some works do not name the artists involved.

When there is an artist included in the metadata (for example here ) this snippet effectively pulls it:

jsonObj['data'][0]['creators'][0]['description']

When there is not an artist in the metadata (for example here ), I get a

TypeError: jsonObj.data[0].creators[0] is undefined

error.

The internet suggests that this is a perfect time to use a try/catch statement:

var data_author = tryCatch(jsonObj['data'][0]['creators'][0]['description'])

var function_image_data = [data_author]

function tryCatch(json_address) {
    try {
         output_json_data = json_address
     }
     catch (e) {
         output_json_data = ''

     }

      return output_json_data
  }

While that works when there is an entry for the author, it appears to have no impact when there is an error. What incredibly obvious thing am I missing from this statement?

Thank you!

EDIT: Based on tex's suggestions below, I moved the attempt to get data out of the function and directly into the code. I'm not entirely sure why it works, but it does avoid the possibility that things are being evaluated before they hit the function. The section that searches for all of the elements of a work now looks like:

    var data_tombstone = tryCatch(jsonObj['data'][0]['tombstone'])
    console.log(data_tombstone)
    var data_title = tryCatch(jsonObj['data'][0]['title'])
    try {
         data_author = jsonObj['data'][0]['creators'][0]['description']
     }
     catch (e) {
         data_author = ''

     }
    var data_creation_date = tryCatch(jsonObj['data'][0]['creation_date'])

Answer 1

jsonObj['data'][0]['creators'][0]['description'] is being evaluated before your tryCatch function is ever called, which means the error won't be caught.

If you're open to using a library, I suggest Ramda . Here's a solution using Ramda (that doesn't involve try..catch :

 const works = { data: [{ creators: [{ description: 'an author'}] }] } const doesntWork = { data: [{ creators: [] }] } const getAuthor = R.pathOr('', ['data', 0, 'creators', 0, 'description']) const data_author_works = getAuthor(works) const data_author_doesnt_work = getAuthor(doesntWork) console.log('works: ', data_author_works) console.log('doesn\\'t work: ', data_author_doesnt_work)

 <script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>

If you don't want to use a library, and do want to use try...catch , you'll need to do something like this, but I wouldn't recommend this approach:

 const works = { data: [{ creators: [{ description: 'an author'}] }] } const doesntWork = { data: [{ creators: [] }] } const getAuthor = jsonData => { try { return jsonData.data[0].creators[0].description } catch (e) { return '' } } const data_author_works = getAuthor(works) const data_author_doesnt_work = getAuthor(doesntWork) console.log('works: ', data_author_works) console.log('doesn\\'t work: ', data_author_doesnt_work)