Clear | Remove | Delete Managed metadata (Taxanomy) column value in SharePoint List/ library

You may find many references to write into taxonomy columns (aka. managed metadata columns) but the clearing those is pretty much tricky.

Following code sample guide you through how you can clear the taxonomy column value in you custom client side application (JSOM) based on SharePoint.

[code type="javascript"]
//USAGE:
//clearWithValue =true => for clear saved taxanomy column values
//clearWithValue =false => wite into taxanomy column

function saveValuesToManagedMetadataColumns(listName, fieldId, taxanomyLabel, siteUrl, clearWithValue) {

//You many need seperate function to resolve GUID for the lable.
//Its based on your requirement and for now its hardcoded
var taxonmyGuid = "9f75f519-51f8-4723-9182-7e8225a54031";
//Loading context and list
var context = new SP.ClientContext(siteUrl);
var list = context.get_web().get_lists().getByTitle(listName);
//Getting item to update
var camlQuery = new SP.CamlQuery();
camlQuery.set_viewXml("<View>" +
"<Query>" +
"<Where><Eq>" +
"<FieldRef Name=\'ID\'/>" +
"<Value Type=\'Number\'>" + fieldId + "</Value>" +
"</Eq></Where>" +
"</Query>" +
"</View>");
var items = list.getItems(camlQuery);
//Load selected items to context
context.load(items);
//Loading MMS field
var field = list.get_fields().getByInternalNameOrTitle("taxanomyColumnName");
var txField = context.castTo(field, SP.Taxonomy.TaxonomyField);
//Load field to context
context.load(txField);

context.executeQueryAsync(function () {
//getting term set ID
var functionTermSetId = txField.get_termSetId().toString();
//Term value build for update..this is not useful is your purpose only for clearing
//But for illustration..got below also to show off
var termValue = new SP.Taxonomy.TaxonomyFieldValue();
termValue.set_label(taxanomyLabel);
termValue.set_termGuid(taxonmyGuid);
termValue.set_wssId(-1);
//Iterate through collection and update
var e = items.getEnumerator();
while (e.moveNext()) {
var item = e.get_current();

//Save to taxanomy column
if (clearWithValue == false)
txField.setFieldValueByValue(item, termValue);

//Clering taxanomy column
if (clearWithValue == true)
txField.validateSetValue(item, null);

//Set noraml fields..If you have them too
item.set_item('Title', metadataCollection.Title);

item.update();
}
context.executeQueryAsync(function (sender, args) {
console.log('Successfully updated item with ', args, serviceId, false);
}, function (args) {
console.log('Error on updating item with taxanomy value', args, serviceId, false);
});

}, function (args) {
console.log('Internal server Error on updating item with taxanomy metadata', args, serviceId, false);
});

}
[/code]
References
http://sharepoint.stackexchange.com/questions/47719/how-can-i-set-empty-value-to-taxonomyfield-of-microsoft-sharepoint-client-taxono