Add "iterateTokenByValue" method

Closes gh-597

lib/js-file.js

@@ -275,6 +275,26 @@ JsFile.prototype = {
             }
         });
     },
+    /**
+     * Iterates token by value from the token array.
+     * Calls passed function for every matched token.
+     *
+     * @param {String|String[]} name
+     * @param {Function} cb
+     */
+    iterateTokenByValue: function(name, cb) {
+        var names = (typeof name === 'string') ? [name] : name;
+        var nameIndex = {};
+        names.forEach(function(type) {
+            nameIndex[type] = true;
+        });
+
+        this.getTokens().forEach(function(token, index, tokens) {
+            if (nameIndex[token.value]) {
+                cb(token, index, tokens);
+            }
+        });
+    },
     /**
      * Returns string representing contents of the file.
      *

test/js-file.js

@@ -134,4 +134,35 @@ describe('modules/js-file', function() {
         assert(ifToken.type === 'Keyword');
         assert(ifToken.value === 'if');
     });
+
+    it('should find token by value', function() {
+        var str = 'if (true);';
+        var file = new JsFile(null, str, esprima.parse(str, {loc: true, range: true, tokens: true}));
+
+        file.iterateTokenByValue(')', function(token, index, tokens) {
+            assert(token.value === ')');
+            assert(index === 3);
+            assert(Array.isArray(tokens));
+        });
+    });
+
+    it('should find tokens by value', function() {
+        var str = 'if (true);';
+        var file = new JsFile(null, str, esprima.parse(str, {loc: true, range: true, tokens: true}));
+
+        file.iterateTokenByValue([')', '('], function(token, index, tokens) {
+            assert(token.value === ')' || token.value === '(');
+            assert(index === 3 || index === 1);
+            assert(Array.isArray(tokens));
+        });
+    });
+
+    it('should not find string value', function() {
+        var str = '"("';
+        var file = new JsFile(null, str, esprima.parse(str, {loc: true, range: true, tokens: true}));
+
+        file.iterateTokenByValue('(', function(token, index, tokens) {
+            assert(false);
+        });
+    });
 });