Question

Having trouble with accessing json values formed from php array

var latlag = '<?php echo json_encode($coordinates); ?>';

alert(latlng) produces:

[{
  "1280":{"lat":"-1.197070","lng":"-1.197070"},
  "1239":{"lat":"-1.222410","lng":"-1.222410"},
  "1258":{"lat":"-1.153020","lng":"-1.153020"},
...
}]

I’ve tried all sorts of ways to access lat and lag for a specific ID and the only result other than undefined has been the nth character of latlng as if its being treated like a string?!

alert(latlng[10]); # {
alert(latlng[1280]['lat]); # undefined 
alert(latlng['1280'].lat); # undefined

Answer 1

You don’t want to put the JSON in quotes, so:

var latlag = <?php echo json_encode($coordinates); ?>;

(Technically, that’s not JSON at all, it’s a JavaScript object initializer. But that’s fine, JSON is a subset of initializer syntax and so all valid JSON texts are also valid JavaScript initializers.)

If the structure is really as you’ve quoted it, it’s an array with one entry, which is an object with properties with names like 1280 and 1258, whose values are objects with properties named lat and lng. So you’d access those like this:

alert(latlng[0]["1280"].lat);

latlng is the array, latlng[0] is the one object it holds, and latlng[0]["1280"] is the {"lat":"-1.197070","lng":"-1.197070"} object.

You may be wondering why I’ve used quotes around 1280 above. It’s because those keys are clearly given as strings (as is required in JSON, though not in JavaScript initializers), and so I can’t be sure there aren’t entries like "0012". Property names are always strings even when not written as strings, so latlng[0][1280] and latlng["0"]["1280"] both mean the same thing (because the 0 and the 1280 are converted to string [yes, really]), but naturally latlng[0]["0012"] is not the same as latlng[0][12] because the latter uses "12", not "0012", as the property name. If you know you won’t have leading zeros, you can ditch the quotes.