Loop through JSON objects that only start with a certain pattern

Question

What is the correct/idiomatic way to loop through JSON objects that only start with a certain pattern?

Example: say I have a JSON like

{
  "END": true, 
  "Lines": "End Reached", 
  "term0": {
    "PrincipalTranslations": {
      // nested data here
    }
  },
  "term1": {
    "PrincipalTranslations": {
      // more nested data here
    }
  }
}

I only want to access the PrincipalTranslations object and I tried with:

$.each(translations, function(term, value) {
    $.each(term, function(pos, value) {
        console.log(pos);
    });
});

Which doesn't work, possibly because I can't loop through the END and Lines objects.

I tried to go with something like

$.each(translations, function(term, value) {
    $.each(TERM-THAT-STARTS-WITH-PATTERN, function(pos, value) {
        console.log(pos);
    });
});

using wildcards, but without success. I could try to mess up with if statements but I suspect there is a nicer solution I'm missing out on. Thanks.

you can't use wildcards there, $.each simply loops over an array or an object's keys. You'll have to do the filtering using something else, such as an if statement. — user400654
– user400654, Commented Jun 2, 2014 at 15:39
If possible, it would be much easier to change your JSON structure. Can you change the format to contain an array of terms instead of each having it's own property? — Rory McCrossan
– Rory McCrossan, Commented Jun 2, 2014 at 15:40
FYI, value will be the object to iterate over, term is the property name. Check the documentation: api.jquery.com/jquery.each — Felix Kling
– Felix Kling, Commented Jun 2, 2014 at 15:43
I get that JSON as a result of an API request so yep, I could re-arrange the whole thing backend-side. Since I'm new to web dev I just assumed the API was right and the problem was me though :] — laurids
– laurids, Commented Jun 2, 2014 at 15:51

Peter van der Wal · Accepted Answer · 2014-06-02 15:46:18Z

3

If you're only interested in the PrincipalTranslations-objects, following would do the trick:

$.each(translations, function(term, value) {
    if (value.PrincipalTranslations !== undefined) {
        console.log(value.PrincipalTranslations);
    }
});

JSFiddle

answered Jun 2, 2014 at 15:46

Peter van der Wal

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Comments

Dalorzo · Accepted Answer · 2014-06-02 15:56:32Z

1

How I would search for a property in an object it is like this:

var obj1 ={ /* your posted object*/};


// navigates through all properties
var x = Object.keys(obj1).reduce(function(arr,prop){
// filter only those that are objects and has a property named "PrincipalTranslations"
    if(typeof obj1[prop]==="object" &&  Object.keys(obj1[prop])
        .filter(
            function (p) {
                return p === "PrincipalTranslations";})) {
                     arr.push(obj1[prop]);
                }
    return arr;
},[]);

console.log(x);

edited Jun 2, 2014 at 15:56

answered Jun 2, 2014 at 15:51

Dalorzo

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4 Comments

laurids Over a year ago

That's interesting, thanks. If I decide to rearrange the API response, would you say is better to do it client-side as in your example or server-side?

Dalorzo Over a year ago

@laurids this works on any browser older than IE9 and if you polyfill on any browser

laurids Over a year ago

actually I was more concerned about which one is the "good practice" rather than portability ;)

Dalorzo Over a year ago

This approach uses ES5 standards. If you want to use jQuery, Underscore or lodash it will depend on the library to provide "portability" probably about the same coverage these days.

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