Merge pull request #65 from bem-sdk/issue-64

feat(isBemEntityName): add `isBemEntityName` method

Author: blond

README.md

@@ -105,6 +105,7 @@ API
 * [isEqual(entityName)](#isequalentityname)
 * [toString()](#tostring)
 * [valueOf()](#valueof)
+* [isBemEntityName()](#isbementityname)
 
 ### constructor(obj)
 
@@ -193,7 +194,6 @@ Parameter    | Type            | Description
 -------------|-----------------|-----------------------
 `entityName` | `BemEntityName` | The entity to compare.
 
-
 Determines whether specified entity is the deepEqual entity.
 
 ```js
@@ -233,6 +233,23 @@ name.valueOf();
 // ➜ { block: 'button', mod: { name: 'focused', value: true } }
 ```
 
+### isBemEntityName()
+
+Determines whether specified entity is instance of BemEntityName.
+
+Parameter    | Type            | Description
+-------------|-----------------|-----------------------
+`entityName` | `BemEntityName` | The entity to check.
+
+```js
+const BemEntityName = require('@bem/entity-name');
+
+const entityName = new BemEntityName({ block: 'input' });
+
+BemEntityName.isBemEntityName(entityName); // true
+BemEntityName.isBemEntityName({}); // false
+```
+
 Debuggability
 -------------
 

index.js

@@ -47,6 +47,8 @@ module.exports = class BemEntityName {
         } else if (modObj || hasModVal) {
             throw new Error('This is not valid BEM entity: the field `mod.name` is undefined.');
         }
+
+        this.__isBemEntityName__ = true;
     }
 
     /**
@@ -256,4 +258,22 @@ module.exports = class BemEntityName {
     isEqual(entityName) {
         return entityName && (this.id === entityName.id);
     }
+
+    /**
+     * Determines whether specified entity is instance of BemEntityName.
+     *
+     * @param {BemEntityName} entityName - the entity to check.
+     *
+     * @returns {boolean} A Boolean indicating whether or not specified entity is instance of BemEntityName.
+     * @example
+     * const BemEntityName = require('@bem/entity-name');
+     *
+     * const entityName = new BemEntityName({ block: 'input' });
+     *
+     * BemEntityName.isBemEntityName(entityName); // true
+     * BemEntityName.isBemEntityName({}); // false
+     */
+    static isBemEntityName(entityName) {
+        return entityName && entityName.__isBemEntityName__;
+    }
 };

test/is-bem-entity-name.test.js

@@ -0,0 +1,17 @@
+const test = require('ava');
+
+const BemEntityName = require('../index');
+
+test('should check valid entities', t => {
+    const entityName = new BemEntityName({ block: 'block' });
+
+    t.true(BemEntityName.isBemEntityName(entityName));
+});
+
+test('should not pass invalid blocks', t => {
+    t.falsy(BemEntityName.isBemEntityName(new Array()));
+});
+
+test('should not pass null', t => {
+    t.falsy(BemEntityName.isBemEntityName(null));
+});