Map with empty values are omitted by default

aurajavascriptlightning-aura-componentsmap

Below is the way I store the keys and values in my map.

Map<String, Object> mapNew = new Map<String, Object>();
Object obj = record.get(fieldName) != null ? record.get(fieldName) : null;    
mapNew.put(fieldMap.get(fieldName).getDescribe().getLabel(), obj); // contains field label and corresponding field value

Response in system.debug is

recordDetail={Account Name=Test, Active=true, Business Phone=null, [email protected], Title=Mr.}

But when I am printing the same map on the javascript side, response looks like this,

Account Name: "Test"
Active: true
Email: "[email protected]"
Title: "Mr."

I want to know why the key with an empty value entry gets omitted automatically and how to handle this issue in javascript side.

Best Answer

I don't know the specifics as to why key's with null values in maps are omitted when passing data to the client, but, a simple enough operation would be to convert your map to a string. Then, from the client, when receiving the server payload, simply use JSON.parse(variable) in order to convert back to an object.

Related Solutions

[SalesForce] Add map values in lightning component

You have to do this "manually":

newMap.forEach((value,key)=>CheckedRecsMap.set(value,key));

Or, you could use an Object instead, which works out more like this:

var CheckedRecsObj = component.get("v.CheckedRecsObj");
var newMap = { arg1: 'value1', arg2: 'value2' };
Object.assign(CheckedRecsObj, newMap);

Set values of map in lightning component

You need to use the set method to set a value in a Map:

mapAcc.set(accId[i].substring(0,18), accName[i].split(',')[0]);

Using the object[key] notation instead sets Object properties on the Map that are not part of the Map's data structure, as noted on MDN:

Setting Object properties works for Map objects as well, and can cause considerable confusion.

Therefore, this appears to work in a way:
const wrongMap = new Map();
wrongMap['bla'] = 'blaa';
wrongMap['bla2'] = 'blaaa2';

console.log(wrongMap); // Map { bla: 'blaa', bla2: 'blaaa2' }
But that way of setting a property does not interact with the Map data structure. It uses the feature of the generic object. The value of 'bla' is not stored in the Map for queries. Other operations on the data fail:
wrongMap.has('bla')    // false
wrongMap.delete('bla') // false
console.log(wrongMap)  // Map { bla: 'blaa', bla2: 'blaaa2' }
The correct usage for storing data in the Map is through the set(key, value) method.

Best Answer

Related Solutions

[SalesForce] Add map values in lightning component

Set values of map in lightning component

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