isTrueish

docs/underscore.function.predicates.js.md

@@ -294,6 +294,28 @@ _.isSequential(new Date);
 
 --------------------------------------------------------------------------------
 
+#### isTrueish
+
+**Signature:** `_.isTrueish(value:String)`
+
+Checks whether an optional string parses to `true` with JSON. Lowercases variable before checking to ensure strings like `"True"` evaluate properly.
+
+```javascript
+_.isTrueish();
+// => false
+
+_.isTrueish(true);
+// => true
+
+_.isTrueish('true');
+// => true
+
+_.isTrueish('FaLsE');
+// => false
+```
+
+--------------------------------------------------------------------------------
+
 #### isValidDate
 
 **Signature:** `_.isValidDate(value:Any)`
@@ -333,4 +355,4 @@ _.isZero("Pythagoras");
 
 --------------------------------------------------------------------------------
 
-[momentjs]:http://momentjs.com/
+[momentjs]:http://momentjs.com/

docs/underscore.util.strings.js.md

@@ -95,4 +95,4 @@ _.toQuery({ forms: { perfect: "circle", imperfect: "square" } });
 // => "forms%5Bperfect%5D=circle&forms%5Bimperfect%5D=square"
 ```
 
---------------------------------------------------------------------------------
+--------------------------------------------------------------------------------

test/function.predicates.js

@@ -239,6 +239,22 @@ $(document).ready(function() {
     assert.equal(_.isDecreasing.apply(null, decNM), false, 'should identify when its arguments monotonically decrease');
   });
 
+  QUnit.test('isTrueish', function(assert) {
+    assert.equal(_.isTrueish(), false, 'should return false');
+    assert.equal(_.isTrueish(undefined), false, 'should return false');
+    assert.equal(_.isTrueish(null), false, 'should return false');
+    assert.equal(_.isTrueish(true), true, 'should return true');
+    assert.equal(_.isTrueish(false), false, 'should return false');
+    assert.equal(_.isTrueish(1), true, 'should return true');
+    assert.equal(_.isTrueish(0), false, 'should return false');
+    assert.equal(_.isTrueish({}), false, 'should return false');
+    assert.equal(_.isTrueish('}'), false, 'should return false');
+    assert.equal(_.isTrueish('true'), true, 'should return true');
+    assert.equal(_.isTrueish('false'), false, 'should return false');
+    assert.equal(_.isTrueish('True'), true, 'should return true');
+    assert.equal(_.isTrueish('FaLsE'), false, 'should return false');
+  });
+
   QUnit.test("isValidDate", function(assert) {
     assert.equal(_.isValidDate(new Date), true, 'should recognize a fresh Date instance as valid');
     assert.equal(!_.isValidDate(new Date("bad date")), true, 'should recognize a Date constructed with gibberish');

underscore.function.predicates.js

@@ -103,5 +103,11 @@ _.mixin({
     }
 
     return true;
+  },
+
+  // Checks whether a string is "trueish"
+  isTrueish: function(v) {
+    v = '' + v;
+    return !!(+v) || v.toLowerCase() === 'true';
   }
 });