Add a concat function for concatenating strings

src/ol/expr/expression.js

@@ -95,6 +95,7 @@ ol.expr.lib = {};
  * @enum {string}
  */
 ol.expr.functions = {
+  CONCAT: 'concat',
   EXTENT: 'extent',
   FID: 'fid',
   GEOMETRY_TYPE: 'geometryType',
@@ -108,6 +109,22 @@ ol.expr.functions = {
 };
 
 
+/**
+ * Concatenate strings.  All provided arguments will be cast to string and
+ * concatenated.
+ * @param {...string} var_args Strings to concatenate.
+ * @return {string} All input arguments concatenated as strings.
+ * @this {ol.Feature}
+ */
+ol.expr.lib[ol.expr.functions.CONCAT] = function(var_args) {
+  var str = '';
+  for (var i = 0, ii = arguments.length; i < ii; ++i) {
+    str += String(arguments[i]);
+  }
+  return str;
+};
+
+
 /**
  * Determine if a feature's extent intersects the provided extent.
  * @param {number} minX Minimum x-coordinate value.