Implement Helpers.

See examples/helpers.js / .html for usage.

examples/helpers.html

@@ -0,0 +1,2 @@
+Hi {{name}}.
+Hi {{ucase name}}.

examples/helpers.js

@@ -0,0 +1,8 @@
+var helpers_helpers = {
+  ucase: function(s) {return s.toUpperCase(); }
+};
+
+var helpers = {
+  name: "Chris"
+};
+

examples/helpers.txt

@@ -0,0 +1,2 @@
+Hi Chris.
+Hi CHRIS.

examples/helpers_error.html

@@ -0,0 +1,3 @@
+Hi {{name}}.
+Hi {{ucase name}}.
+Hi {{lcase name}}.

examples/helpers_error.js

@@ -0,0 +1,8 @@
+var helpers_error_helpers = {
+  ucase: function(s) {return s.toUpperCase(); }
+};
+
+var helpers_error = {
+  name: "Chris"
+};
+

examples/helpers_error.txt

@@ -0,0 +1 @@
+ERROR: Helper 'lcase' is not a registered helper

mustache.js

@@ -13,6 +13,7 @@ var Mustache = function() {
     ctag: "}}",
     pragmas: {},
     buffer: [],
+    helper_functions: {},
     pragmas_implemented: {
       "IMPLICIT-ITERATOR": true
     },
@@ -269,7 +270,22 @@ var Mustache = function() {
       }
 
       var value;
-      
+      var helper;
+
+      // check for helper e.g. name = "helperfun name"
+      var helper_name = name.split(" ");
+      if(helper_name.length == 2)  { // we have a helper
+        helper = helper_name[0];
+        name = helper_name[1];
+        if(!this.helper_functions[helper]
+            || typeof this.helper_functions[helper] != "function") {
+          throw {message:
+            "Helper '" + helper + "' is not a registered helper"};
+        } else {
+          helper = this.helper_functions[helper];
+        }
+      }
+
       // check for dot notation eg. foo.bar
       if(name.match(/([a-z_]+)\./ig)){
         var childValue = this.walk_context(name, context);
@@ -286,8 +302,13 @@ var Mustache = function() {
       }
 
       if(typeof value === "function") {
-        return value.apply(context);
+        value = value.apply(context);
       }
+
+      if(helper) {
+        value = helper.apply(context, [value]);
+      }
+
       if(value !== undefined) {
         return value;
       }
@@ -408,11 +429,14 @@ var Mustache = function() {
     /*
       Turns a template and view into HTML
     */
-    to_html: function(template, view, partials, send_fun) {
-      var renderer = new Renderer();
+    to_html: function(template, view, partials, send_fun, helpers) {
+      var renderer = new Renderer(helpers);
       if(send_fun) {
         renderer.send = send_fun;
       }
+      if(helpers) {
+        renderer.helper_functions = helpers;
+      }
       renderer.render(template, view || {}, partials);
       if(!send_fun) {
         return renderer.buffer.join("\n");

test/mustache_spec.rb

@@ -84,9 +84,10 @@ describe "mustache" do
           runner = <<-JS
             try {
               #{@boilerplate}
+              var #{testname}_helpers = null;
               #{view}
               var template = #{template};
-              var result = Mustache.to_html(template, #{testname});
+              var result = Mustache.to_html(template, #{testname}, null, null, #{testname}_helpers);
               print(result);
             } catch(e) {
               print('ERROR: ' + e.message);
@@ -102,6 +103,7 @@ describe "mustache" do
           runner = <<-JS
             try {
               #{@boilerplate}
+              var #{testname}_helpers = null;
               #{view}
               var chunks = [];
               var sendFun = function(chunk) {
@@ -110,7 +112,7 @@ describe "mustache" do
                 }
               }
               var template = #{template};
-              Mustache.to_html(template, #{testname}, null, sendFun);
+              Mustache.to_html(template, #{testname}, null, sendFun, #{testname}_helpers);
               print(chunks.join("\\n"));
             } catch(e) {
               print('ERROR: ' + e.message);
@@ -132,10 +134,11 @@ describe "mustache" do
           runner = <<-JS
             try {
               #{@boilerplate}
+              var #{testname}_helpers = null;
               #{view}
               var template = #{template};
               var partials = {"partial": #{partial}};
-              var result = Mustache.to_html(template, partial_context, partials);
+              var result = Mustache.to_html(template, partial_context, partials, null, #{testname}_helpers);
               print(result);
             } catch(e) {
               print('ERROR: ' + e.message);
@@ -152,7 +155,8 @@ describe "mustache" do
           runner = <<-JS
             try {
               #{@boilerplate}
-              #{view};
+              var #{testname}_helpers = null;
+              #{view}
               var template = #{template};
               var partials = {"partial": #{partial}};
               var chunks = [];
@@ -161,7 +165,7 @@ describe "mustache" do
                   chunks.push(chunk);
                 }
               }
-              Mustache.to_html(template, partial_context, partials, sendFun);
+              Mustache.to_html(template, partial_context, partials, sendFun, #{testname}_helpers);
               print(chunks.join("\\n"));
             } catch(e) {
               print('ERROR: ' + e.message);