Add an is_operation method

logic.js

@@ -181,6 +181,29 @@ http://ricostacruz.com/cheatsheets/umdjs.html
     );
   };
 
+  jsonLogic.is_operation = function(op) {
+    if (typeof op !== "string") {
+      return false;
+    }
+    if (operations.hasOwnProperty(op) && typeof operations[op] === "function") {
+      return true;
+    } else if (["if", "?:", "and", "or", "filter", "map", "reduce", "all", "none", "some", "@"].indexOf(op) !== -1) {
+      return true;
+    } else if (op.indexOf(".") > 0) {
+      var sub_ops = String(op).split(".");
+      var operation = operations;
+      for (var i = 0; i < sub_ops.length; i++) {
+        if (!operation.hasOwnProperty(sub_ops[i])) {
+          return false;
+        }
+        // Descending into operations
+        operation = operation[sub_ops[i]];
+      }
+      return true;
+    }
+    return false;
+  };
+
   /*
   This helper will defer to the JsonLogic spec as a tie-breaker when different language interpreters define different behavior for the truthiness of primitives.  E.g., PHP considers empty arrays to be falsy, but Javascript considers them to be truthy. JsonLogic, as an ecosystem, needs one consistent answer.
 

tests/tests.js

@@ -307,4 +307,48 @@ QUnit.module('basic', () => {
     jsonLogic.apply({"or": [{"push": [true]}, {"push": [true]}]});
     assert.deepEqual(i, [true]);
   });
+
+  QUnit.test( "Expanding functionality with is_operation ", function(assert) {
+    // Operations that are set directly on the operations variable.
+    var declaredOperations = ["!!", "!", "!=", "!==", "%", "*", "+", "-", "/", "<", "<=", "==", "===", ">", ">=", "cat", "in", "log", "max", "merge", "min", "missing", "missing_some", "substr", "var"];
+    declaredOperations.forEach((operationName) => {
+      assert.equal(jsonLogic.is_operation(operationName), true, `is_operation should consider this an operation but it is NOT: ${operationName}`);
+    });
+
+    // Operations that are NOT set directly on the operations variable.
+    var undeclaredOperations = ["if", "?:", "and", "or", "filter", "map", "reduce", "all", "none", "some", "@"];
+    undeclaredOperations.forEach((operationName) => {
+      assert.equal(jsonLogic.is_operation(operationName), true, `is_operation should consider this an operation but it is NOT: ${operationName}`);
+    });
+
+    // Handle all the absurd inputs.
+    var notOperations = [[], undefined, null, NaN, '', true, false, {}, {"var":"value"}, new Error(), Error];
+    notOperations.forEach((operationName) => {
+      assert.equal(jsonLogic.is_operation(operationName), false, `is_operation should NOT consider this an operation but it is: ${operationName}`);
+    });
+
+    // A custom operation should not exist before it should, then it should exist.
+    var custom_operation = function(a) {
+      return a;
+    };
+    assert.equal(jsonLogic.is_operation('custom_operation'), false, 'is_operation should NOT consider this an operation but it is: custom_operation');
+    jsonLogic.add_operation("custom_operation", custom_operation);
+    assert.equal(jsonLogic.is_operation('custom_operation'), true, 'is_operation should consider this an operation but it is NOT: custom_operation');
+
+    // A custom operation using dot notation should not exist before it should,
+    // then it should exist. And, non-existing dot notation operations should
+    // not be considered operations.
+    var nested_operation = function(a) {
+      return a;
+    };
+    nested_operation.sub_operation = function(a) {
+      return a;
+    };
+    assert.equal(jsonLogic.is_operation('nested_operation'), false, 'is_operation should NOT consider this an operation but it is: nested_operation');
+    assert.equal(jsonLogic.is_operation('nested_operation.sub_operation'), false, 'is_operation should NOT consider this an operation but it is: nested_operation.sub_operation');
+    jsonLogic.add_operation("nested_operation", nested_operation);
+    assert.equal(jsonLogic.is_operation('nested_operation'), true, 'is_operation should consider this an operation but it is NOT: nested_operation');
+    assert.equal(jsonLogic.is_operation('nested_operation.sub_operation'), true, 'is_operation should consider this an operation but it is NOT: nested_operation.sub_operation');
+    assert.equal(jsonLogic.is_operation('nested_operation.not_an_operation'), false, 'is_operation should NOT consider this an operation but it is: nested_operation.not_an_operation');
+  });
 });