How to retrieve multi-value Taxonomy Field from term store SharePoint online

Question

I am trying to retrieve terms from term store using JavaScript, it work just a fine with this code: Get the label of single taxonomy field:

var fieldValue = item.get_item("FieldName");
var fieldLabel = fieldValue.Label;

I have one issue to retrieve labels of a multi-value Taxonomy Field? I've tried this

var fieldValue = item.get_item("FieldName");
var taxEnumerator = fieldValue.getEnumerator();
while(taxEnumerator.moveNext()){
    var currentTerm = taxEnumerator.get_current();
    var label = currentTerm.Label;
    // do something with the label here
}

But it doesn't work

Answer 1

Most likely you are getting this error since sp.taxonomy.js library has not been loaded and in that case taxonomy field value is returned as "lightweight" object (not of SP.Taxonomy.TaxonomyFieldValueCollection object type).

Option 1 (recommended): getting getting multiple taxonomy field values with sp.taxonomy library

First of all, I would recommend this approach since SP.Taxonomy namespace provides not only a standard way for dealing with taxonomy field values but also a way of working with Managed Metadata API via JSOM.

The following example shows how to:

• ensure sp.taxonomy.js library has been loaded
• get multiple taxonomy field value which represents SP.Taxonomy.TaxonomyFieldValueCollection object

Example:

SP.SOD.registerSod('sp.taxonomy.js', SP.Utilities.Utility.getLayoutsPageUrl('sp.taxonomy.js'));   
SP.SOD.executeFunc('sp.taxonomy.js', 'SP.Taxonomy.TaxonomySession', function () { 

var ctx = SP.ClientContext.get_current();
var list = ctx.get_web().get_lists().getByTitle(listTitle);
var item = list.getItemById(itemId);
ctx.load(item);

ctx.executeQueryAsync(
   function(){

      var fieldVal = item.get_item(fieldName); 

      for(var i = 0; i < fieldVal.get_count(); i++) {
         var label = fieldVal.get_item(i).get_label();
         var guid = fieldVal.get_item(i).get_termGuid();
         //...
      }       
   },
   function(sender,args){
       console.log(args.get_message());
   });


});

Option 2: getting multiple taxonomy field values without sp.taxonomy.js library loaded

When sp.taxonomy library is not loaded, taxonomy field value could still be retrieved via _Child_Items_ property as demonstrated below:

var ctx = SP.ClientContext.get_current();
var list = ctx.get_web().get_lists().getByTitle(listTitle);
var item = list.getItemById(itemId);
ctx.load(item);

ctx.executeQueryAsync(
   function(){

      var fieldVal = item.get_item(fieldName)._Child_Items_; 
      for(var i = 0; i < fieldVal.length; i++) {
         var label = fieldVal[i].Label;
         var guid = fieldVal[i].TermGuid;
         //...
      }       
   },
   function(sender,args){
       console.log(args.get_message());
   });