How to check for presence of 'key' in jq before iterating over the values

I get Cannot iterate over null (null) from the below query because .property_history is not present in result object.

How do i check for the presence of .property_history key before proceeding with map(...) ?

I tried using something like sold_year= `echo "$content" | jq 'if has("property_history") then map(select(.event_name == "Sold"))[0].date' else null end

Original Query:

sold_year=`echo "$content" | jq '.result.property_history | map(select(.event_name == "Sold"))[0].date'`

JSON:

{  
   "result":{  
      "property_history":[  
         {  
            "date":"01/27/2016",
            "price_changed":0,
            "price":899750,
            "event_name":"Listed",
            "sqft":0
         },
         {  
            "date":"12/15/2015",
            "price_changed":0,
            "price":899750,
            "event_name":"Listed",
            "sqft":2357
         },
         {  
            "date":"08/30/2004",
            "price_changed":0,
            "price":739000,
            "event_name":"Sold",
            "sqft":2357
         }
      ]
   }
}

You can use the select-expression in jq to do what you intend to achieve, something as,

jq '.result 
  | select(.property_history != null) 
  | .property_history 
  | map(select(.event_name == "Sold"))[0].date'

Technically, to test for the presence of a property, you should use has/1, but in the present context, it would probably be better to use the postfix ? operator, e.g.:

$ jq '.result 
  | .property_history[]?
  | select(.event_name == "Sold") 
  | .date'
"08/30/2004"

use has("mykey1") (for objects) or has(0) (for arrays):

jq 'has("name")' <<< "{\"name\": \"hello\"}"

output:

true

The trick is to use // together with empty:

jq '.result.property_history // empty | map(select(.event_name == "Sold"))[0:1][].date'

Another alternative is to use an additional select:

jq '.result.property_history | select(.) | map(select(.event_name == "Sold"))[0:1][].date'

General pattern:

try (...) // "default_value"

With your logic:

jq 'try (.result.property_history | map(select(.event_name == "Sold"))[0].date) // "default_value"'

try (without a catch) returns empty if the expression fails. // provides a default value if the value is empty.