1 files changed, 51 insertions, 0 deletions
diff --git a/build-tools/lib/less/tree/javascript.js b/build-tools/lib/less/tree/javascript.js
new file mode 100644
index 00000000..4ec66b9e
--- /dev/null
+++ b/build-tools/lib/less/tree/javascript.js
@@ -0,0 +1,51 @@
+(function (tree) {
+
+tree.JavaScript = function (string, index, escaped) {
+    this.escaped = escaped;
+    this.expression = string;
+    this.index = index;
+};
+tree.JavaScript.prototype = {
+    eval: function (env) {
+        var result,
+            that = this,
+            context = {};
+
+        var expression = this.expression.replace(/@\{([\w-]+)\}/g, function (_, name) {
+            return tree.jsify(new(tree.Variable)('@' + name, that.index).eval(env));
+        });
+
+        try {
+            expression = new(Function)('return (' + expression + ')');
+        } catch (e) {
+            throw { message: "JavaScript evaluation error: `" + expression + "`" ,
+                    index: this.index };
+        }
+
+        for (var k in env.frames[0].variables()) {
+            context[k.slice(1)] = {
+                value: env.frames[0].variables()[k].value,
+                toJS: function () {
+                    return this.value.eval(env).toCSS();
+                }
+            };
+        }
+
+        try {
+            result = expression.call(context);
+        } catch (e) {
+            throw { message: "JavaScript evaluation error: '" + e.name + ': ' + e.message + "'" ,
+                    index: this.index };
+        }
+        if (typeof(result) === 'string') {
+            return new(tree.Quoted)('"' + result + '"', result, this.escaped, this.index);
+        } else if (Array.isArray(result)) {
+            return new(tree.Anonymous)(result.join(', '));
+        } else {
+            return new(tree.Anonymous)(result);
+        }
+    }
+};
+
+})(require('less/tree'));
+