If your shell supports process substitution (Bash-style follows, see docs):

diff <(jq --sort-keys . A.json) <(jq --sort-keys . B.json)

Objects key order will be ignored, but array order will still matter. It is possible to work-around that, if desired, by sorting array values in some other way, or making them set-like (e.g. ["foo", "bar"] → {"foo": null, "bar": null}; this will also remove duplicates).

Alternatively, substitute diff for some other comparator, e.g. cmp, colordiff, or vimdiff, depending on your needs. If all you want is a yes or no answer, consider using cmp and passing --compact-output to jq to not format the output for a potential small performance increase.

Use jq to first sort all keys. Then diff to do the diffing:

jq -S . A.json > A-sorted.json
jq -S . B.json > B-sorted.json
diff A-sorted.json B-sorted.json

The above example is for Linux but both jq and diff is available for Windows. It seems Windows has an alternative diff tool called fc, perhaps this could be used instead of diff.

You can run both files through jq (available as a small Windows binary), let jq pretty-print and sort the data in both files according to your needs, and then perform an "ordinary" diff (with WinDiff, Meld, Diffuse).

the shell commands would be

 < file1.json jq  'keys' > file1.sorted.json
 < file2.json jq  'keys' > file2.sorted.json

diff file1.sorted.json file2.sorted.json

# or better

diff -q file1.sorted.json file2.sorted.json

#
#       -q, --brief
#              report only when files differ

# if output of diff -q is nonempty, files differ -> raise an error

If you know what's going on, continue with the unmodified files.

This obviously works only if the JSON objects differ only in their keys. This also assumes that the type info is preserved (e.g. the string representation of floats does not differ between the two files)

If the JSON objects differ in object values, or if the values contain nested objects (which themselves can differ in values or in subkey ordering), or if you want the order of the first-level-keys unchanged, but need to only compare the nested "value-objects" by some other criterion, you will need more complicated jq commands.
Check stackoverflow.com - some incredible jq experts there.

It's not too hard to create a function like this. Just loop through each field in the second object, and if it's not present in the first or the value is different than the first, put that field in the return object.

var compareJSON = function(obj1, obj2) {
  var ret = {};
  for(var i in obj2) {
    if(!obj1.hasOwnProperty(i) || obj2[i] !== obj1[i]) {
      ret[i] = obj2[i];
    }
  }
  return ret;
};

You can see it in action on this demo page.