Add filter.is_for_only(operand).

frontend_tests/node_tests/filter.js

@@ -711,6 +711,37 @@ function make_sub(name, stream_id) {
     assert.equal(filter.is_stream_only(), false);
     assert.equal(filter.is_stream_topic_only(), false);
     assert.equal(filter.is_pm_with_only(), true);
+    assert.equal(filter.is_for_only('mentioned'), false);
+    assert.equal(filter.is_for_only('private'), false);
+
+    terms = [
+        {operator: 'is', operand: 'private'},
+    ];
+    filter = new Filter(terms);
+    assert.equal(filter.is_for_only('mentioned'), false);
+    assert.equal(filter.is_for_only('private'), true);
+
+    terms = [
+        {operator: 'is', operand: 'mentioned'},
+    ];
+    filter = new Filter(terms);
+    assert.equal(filter.is_for_only('mentioned'), true);
+    assert.equal(filter.is_for_only('private'), false);
+
+    terms = [
+        {operator: 'is', operand: 'mentioned'},
+        {operator: 'is', operand: 'starred'},
+    ];
+    filter = new Filter(terms);
+    assert.equal(filter.is_for_only('mentioned'), false);
+    assert.equal(filter.is_for_only('private'), false);
+
+    terms = [
+        {operator: 'is', operand: 'mentioned', negated: true},
+    ];
+    filter = new Filter(terms);
+    assert.equal(filter.is_for_only('mentioned'), false);
+    assert.equal(filter.is_for_only('private'), false);
 }());
 
 (function test_update_email() {

static/js/filter.js

@@ -433,6 +433,28 @@ Filter.prototype = {
         return (term.operator === 'pm-with');
     },
 
+    is_for_only: function (operand) {
+        // Call as:
+        //    filter.is_for_only('mentioned')
+        //    filter.is_for_only('private')
+        //    filter.is_for_only('starred')
+        if (this._operators.length !== 1) {
+            return false;
+        }
+
+        var term = this._operators[0];
+
+        if (term.negated) {
+            return false;
+        }
+
+        if (term.operator !== 'is') {
+            return false;
+        }
+
+        return (term.operand === operand);
+    },
+
     update_email: function (user_id, new_email) {
         _.each(this._operators, function (term) {
             switch (term.operator) {