I have a object defined as
{ "query" : { /* snip */ }, "aggs": { "times" : { "date_histogram" : { "field" : "@timestamp", "interval" : "15m", "format" : "HH:mm", "min_doc_count" : 0 } } } }; How can I tell whether interval in aggs.times.date_histogram exists, so that I can manipulate it?
Clarification: I can not be sure that any of the parent objects to interval exist.
You can check it with typeof:
if(typeof aggs.times.date_histogram['interval'] !== 'undefined') { // ... exists ... } Another method is using the in keyword (this one is prettier and more obvious imho)
if('interval' in aggs.times.date_histogram) { // ... exists ... } The above is assuming aggs.times.date_histogram exists (and doesn't need an existence check)
Update: For checking the existence of everything leading to the value you need, you can use this:
function getProp(_path, _parent) { _path.split('.').forEach(function(_x) { _parent = (!_parent || typeof _parent !== 'object' || !(_x in _parent)) ? undefined : _parent[_x]; }); return _parent; } You can call it like:
getProp('aggs.times.date_histogram.interval', parent_of_aggs); Will return the value of interval if it is defined, else it will return undefined
getProp() for a couple years without any issues so far. Example: jsfiddle.net/11xrrxo1Assuming the value is always a non-blank string, just test it for truthiness:
if (aggs.times.date_histogram.interval) { // Use it } You might cache the result of those property lookups. Though it's unlikely to really matter for performance, it may be useful for code maintainability:
var interval = aggs.times.date_histogram.interval; if (interval) { // Use it } If you need to worry that each level may not exist, it gets more verbose:
if (aggs && aggs.times && aggs.times.date_histogram && aggs.times.date_histogram.interval) { // Use it } There's a question with several answers about writing a function for that.
.., then you'd do: aggs..times..date_histogram..interval and you'd get undefined, rather than an error, if any level didn't exist. IIRC, it didn't meet the "pulls its syntactic weight" requirement and wasn't advanced. :-| Too bad, in my view, but...test = { "query" : { /* snip */ }, "aggs": { "times" : { "date_histogram" : { "field" : "@timestamp", "interval" : "15m", "format" : "HH:mm", "min_doc_count" : 0 } } } }; Use this:
if(test.aggs.times.date_histogram.interval) { alert('true'); //your code here } else { alert('false'); //your code here } 
