How can I set field value to Null using Web Console ?

Hi, I am using the web console (F12) to update fields such as external id on subsidiary record. I cannot find how to set the value of this field back to Null. Any idea please ?

Here is the command to update :

require([‘N/record’, ‘N/currentRecord’]);

var record = require(‘N/record’);

var currentRecord = require(‘N/currentRecord’);

var myCurrentRecord = currentRecord.get();

var subsidiaryRecord = record.load({
type: record.Type.SUBSIDIARY,
id: myCurrentRecord.id
});

subsidiaryRecord.setValue({
fieldId: ‘externalid’,
value: ‘BBB‘
});

subsidiaryRecord.save();