Add select filter

CHANGELOG.md

@@ -1,6 +1,8 @@
 Changelog
 =========
 
+* Add [`select` filter](https://mozilla.github.io/nunjucks/templating.html#select).
+
 3.2.1 (Mar 17 2020)
 -------------------
 * Replace yargs with commander to reduce number of dependencies. Merge of

docs/templating.md

@@ -1572,6 +1572,33 @@ escaping enabled this variable will not be escaped.
 foo <a href="http://www.example.com/">http://www.example.com/</a> bar
 ```
 
+### select
+
+Filters a sequence of objects by applying a test to each object, and only
+selecting the objects with the test succeeding.
+
+If no test is specified, each object will be evaluated as a boolean.
+
+**Input**
+
+```jinja
+{% set numbers=[0, 1, 2, 3, 4, 5] %}
+
+{{ numbers | select("odd") | join }}
+{{ numbers | select("even") | join }}
+{{ numbers | select("divisibleby", 3) | join }}
+{{ numbers | select() | join }}
+```
+
+**Output**
+
+```jinja
+135
+024
+03
+12345
+```
+
 ### selectattr (only the single-argument form)
 
 Filter a sequence of objects by applying a test to the specified attribute

nunjucks/src/filters.js

@@ -272,6 +272,17 @@ function rejectattr(arr, attr) {
 
 exports.rejectattr = rejectattr;
 
+function select(arr, testName = 'truthy', secondArg) {
+  const context = this;
+  const test = context.env.getTest(testName);
+
+  return arr.filter(function applyToTest(item) {
+    return test.call(context, item, secondArg);
+  });
+}
+
+exports.select = select;
+
 function selectattr(arr, attr) {
   return arr.filter((item) => !!item[attr]);
 }

tests/filters.js

@@ -504,6 +504,22 @@
       finish(done);
     });
 
+    it('select', function(done) {
+      var context = {
+        numbers: [0, 1, 2, 3, 4, 5]
+      };
+
+      equal('{{ numbers | select("odd") | join }}', context, '135');
+
+      equal('{{ numbers | select("even") | join }}', context, '024');
+
+      equal('{{ numbers | select("divisibleby", 3) | join }}', context, '03');
+
+      equal('{{ numbers | select() | join }}', context, '12345');
+
+      finish(done);
+    });
+
     it('selectattr', function(done) {
       var foods = [{
         tasty: true