javascript - JSON - searching through keys with variable names (unknown)

Question

Total JSON noob here. I'm trying to cycle through some JSON to pull out the first image from an array inside the object, and after 4 hours of having at it, I've decided I probably need some help.

I'm able to pull every value I need out of the object where I know the key, but I have some data that has non consistent key names that I need to basically iterate through looking for a partial match and then pulling the first on of these results.

The Json structure of the unknown element is structured like this:

"custom_fields": {
    "content_0_subheading": [
      "Title text"
    ],
    "content_1_text": [
      "Some text"
    ],
    "content_2_image": [
      [
        "http://staging.livelivelyblog.assemblo.com/wp-content/uploads/2013/09/wellbeing-260x130.jpg",
        260,
        130,
        true
      ]
    ],
    "content_2_caption": [
      ""
        ]
}

What I'm after is the content_2_image in this case, but in another entry it could be content_20_image for all I know (there's a lot of data being pulled).

Any ideas of the best way to cycle through these unknown keys looking for a partial match on '_image' in the key or something, would be VERY appreciated.

Thanks!

Answer 1

You can't just search through every field with a partial match, so you'll have to iterate through every field and then check the field names for the match. Try something like this:

var json = {
  "content_0_subheading": [
    "Title text"
  ],
  "content_1_text": [
    "Some text"
  ],
  "content_2_image": [
    [
      "http://staging.livelivelyblog.assemblo.com/wp-content/uploads/2013/09/wellbeing-260x130.jpg",
      260,
      130,
      true
    ]
  ],
  "content_2_caption": [
    ""
  ]
}

for (var key in json) {
    if (json.hasOwnProperty(key)) {
        if (/content_[0-9]+_image/.test(key)) {
            console.log('match!', json[key]); // do stuff here!
        }
    }
}

Basically, what we're doing is:

1) Loop through keys of json object for (var key in json)

2) Ensure the json has the property, and we're not accessing keys we don't want if (json.hasOwnProperty(key))

3) Check if key matches the regular expression /content_[0-9]+_image/

3a) Basically, test if it matches content_ANY NUMBERS_image where ANY NUMBERS is equal to at least one digit or more

4) Use that data however you please console.log(json[key])

Hope this helps!