set taxonomy field multiple values

Question

I'm creating a sharepoint hosted app which is based on javascript only. I wanted to update a multivalue taxonomy field in a list so I wrote this function which didn't work. there is a very little support for javascript csom online.

var list = context.get_web().get_lists().getByTitle('Company');
var item = list.getItemById(2);

var field = list.get_fields().getByInternalNameOrTitle("Departments");
var taxField = context.castTo(field, SP.Taxonomy.TaxonomyField);

var terms = new SP.Taxonomy.TaxonomyFieldValueCollection(context,
'Unit 1|5bf47d1f-d890-49d1-a844-85628ca508fd;#Unit 4|334ad23d-d2d8-4acb-ab09-38d2bacb97d4',
taxField);

taxField.setFieldValueByValueCollection(item, terms);

item.update();
context.load(taxField);
context.executeQueryAsync(
function() {
    console.log('field updated');
});

I also used this code

var list = context.get_web().get_lists().getByTitle('Company');
var item = list.getItemById(2);

item.set_item('Departments', 'Unit 1|5bf47d1f-d890-49d1-a844-85628ca508fd;Unit 4|334ad23d-d2d8-4acb-ab09-38d2bacb97d4');
item.update();
context.executeQueryAsync(
function() {
    console.log('field updated');
});

Answer 1

You must include a fake wssid (lookup id) prefix to the value. Below is a code I use to set a multiple value term field from jsom in the app model. This works.

function SetManagedMetaDataField() {
appweburl = decodeURIComponent(getQueryStringParameter('SPAppWebUrl'));
hostweburl = decodeURIComponent(getQueryStringParameter('SPHostUrl'));
context = new SP.ClientContext(appweburl);
factory = new SP.ProxyWebRequestExecutorFactory(appweburl);
context.set_webRequestExecutorFactory(factory);
appContextSite = new SP.AppContextSite(context, hostweburl);

var list = appContextSite.get_web().get_lists().getByTitle('Documents');
var item = list.getItemById(5);

var field = list.get_fields().getByInternalNameOrTitle("Cars");
var taxField = context.castTo(field, SP.Taxonomy.TaxonomyField);

var terms = new SP.Taxonomy.TaxonomyFieldValueCollection(context,
'-1;#ATS|9f3e8e20-593b-471d-a145-81ff8664fd96;#-1;#CTS|8b18f6df-22be-4548-92b4-8f240d8fbfe5',
taxField);

taxField.setFieldValueByValueCollection(item, terms);

item.update();
context.load(taxField);
context.executeQueryAsync(
function () {
    alert('field updated');
}, function (sender,args) {
    alert(args.get_message() + '\n' + args.get_stackTrace());
});
}