How can I append an empty array field into a JSON if a JSON field is null?

Question

I am not so into JavaScript and I have this problem (I can solve it only using pure old JS and not third party library).

I have a JavaScript script processing a JSON object, in my script I have:

if(finalResponse.SubSpeciesInfo == null) {
    log.info("NO SUBSPECIES");
    finalResponse.SubSpeciesInfo.SubSpeciesList = [];
}

that check if this property of my original JSON object is null:

"SubSpeciesInfo": null

If this property of my JSON object is null it enter into the if block.

What I have to do here is to append the SubSpeciesList sub field that is an empty list.

But in this way it is not working, I obtain an error like:

 ERROR {org.apache.synapse.mediators.bsf.ScriptMediator} -  The script engine returned an error executing the inlined js script function mediate {org.apache.synapse.mediators.bsf.ScriptMediator}
com.sun.phobos.script.util.ExtendedScriptException: org.mozilla.javascript.EcmaError: TypeError: Cannot set property "SubSpeciesList" of null to "org.mozilla.javascript.NativeArray@37aa205f" (<Unknown Source>#106) in <Unknown Source> at line number 106
        at com.sun.phobos.script.javascript.RhinoCompiledScript.eval(RhinoCompiledScript.java:68)

What is the problem? What am I missing? How can I fix this issue?

Rohìt Jíndal · Accepted Answer · 2018-05-31 17:30:05Z

3

You need to assign an object with a new property for the array, because you try to use a property SubSpeciesList, which does not exist.

if (finalResponse.SubSpeciesInfo === null) {
    log.info("NO SUBSPECIES");
    finalResponse.SubSpeciesInfo = { SubSpeciesList: [] };
}

For a comparison without type coercion use better === for a strict check. Read more: Strict equality using ===

DEMO

var finalResponse = {
  SubSpeciesInfo : null 
}

if(finalResponse.SubSpeciesInfo === null) {
    console.log("NO SUBSPECIES");
    finalResponse.SubSpeciesInfo = {SubSpeciesList : []};
}

console.log(finalResponse);

edited May 31, 2018 at 17:30

Rohìt Jíndal

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answered May 31, 2018 at 15:04

Nina Scholz

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