existsUnless is added

README.md

@@ -67,6 +67,7 @@ The following are the list of all keys that have special meaning in template obj
 - [`arrayContent`](#arrayContent)
 - [`constant`](#constant)
 - [`existsWhen`](#existsWhen)
+- [`existsUnless`](#existsUnless)
 - [`dataTransform`](#dataTransform)
 - [`default`](#default)
 - [`multiple`](#multiple)
@@ -451,7 +452,7 @@ console.log(r); // 'CONST'
 <a name="existsWhen" />
 #### `existsWhen` rule
 
-This rule determines if a property or value exists.  It must be a predicate or array of predicates.  This rule is evaluated before any other rule on the same level.
+This rule must be a predicate or array of predicates. If the predicate evaluates to false, the template is ignored.  This rule is evaluated before any other rule on the same level.
 
 ```js
 var _ = require('lodash');
@@ -496,7 +497,7 @@ var r2 = j2j.run(template, {
 console.log(r2); // null
 ```
 
-If this rule is an array each predicate in the array must evaluate to true
+If this rule is an array, each predicate in the array must evaluate to true
 
 ```js
 var _ = require('lodash');
@@ -537,6 +538,95 @@ console.log(r2.dest_a); // 'value_a'
 console.log(r2.dest_b); // 'value_b'
 ```
 
+<a name="existsUnless" />
+#### `existsUnless` rule
+
+ This rule must be a predicate or array of predicates. If the predicate evaluates to true, the template is ignored.  This rule is evaluated before any other rule but existsWhen.
+
+```js
+var _ = require('lodash');
+
+var template = {
+    content: {
+        dest_a: {
+            dataKey: 'a'
+        },
+        dest_b: {
+            dataKey: 'b',
+            existsUnless: _.partialRight(_.has, 'c')
+        },
+    },
+    existsUnless: function (input) {
+        return input && input.private;
+    }
+};
+
+var r0 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b',
+    c: 0,
+    private: false
+});
+console.log(r0.dest_a); // 'value_a'
+console.log(r0.dest_b); // undefined
+
+var r1 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b'
+});
+console.log(r1.dest_a); // 'value_a'
+console.log(r1.dest_b); // 'value_b'
+
+var r2 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b',
+    private: true
+});
+console.log(r2); // null
+```
+
+If this rule is an array, each predicate in the array must evaluate to true for the template to evaluate to `null`.
+
+```js
+var _ = require('lodash');
+
+var template = {
+    content: {
+        dest_a: {
+            dataKey: 'a'
+        },
+        dest_b: {
+            dataKey: 'b'
+        },
+    },
+    existsUnless: [_.partialRight(_.has, 'c'), _.partialRight(_.has, 'd')]
+};
+
+var r0 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b',
+    c: 'available'
+});
+console.log(r0.dest_a); // 'value_a'
+console.log(r0.dest_b); // 'value_b'
+
+var r1 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b',
+    d: 'available'
+});
+console.log(r1.dest_a); // 'value_a'
+console.log(r1.dest_b); // 'value_b'
+
+var r2 = j2j.run(template, {
+    a: 'value_a',
+    b: 'value_b',
+    c: 'available',
+    d: 'available'
+});
+console.log(r2); // null
+```
+
 <a name="dataTransform" />
 #### `dataTransform` rule
 

RELEASENOTES.md

@@ -3,6 +3,8 @@
 - dataKeyPieceOverride functionality is removed
 - paths like 'a.b.c' where 'b' is array is not supported. use a.b[*].c with jsonave.
 - 'dataKeyFnOptions' replaced with 'context' option.
+- existsWhen now accepts arrays.
+- existsUnless is added.  Opposite of existsWhen
 
 # v1.5.0 - June 12, 2015
 

lib/json2json.js

@@ -131,19 +131,39 @@ var prototype = {
             return null;
         }
     },
-    run: function (template, input) {
-        if (template.existsWhen) {
-            if (Array.isArray(template.existsWhen)) {
-                var ewCheck = template.existsWhen.every(function (ew) {
+    evaluateExistsWhen: function (template, input) {
+        var existsWhen = template.existsWhen;
+        if (existsWhen) {
+            if (Array.isArray(existsWhen)) {
+                return existsWhen.every(function (ew) {
                     return ew(input);
                 });
-                if (!ewCheck) {
-                    return null;
-                }
-            } else if (!template.existsWhen(input)) {
-                return null;
+            } else {
+                return existsWhen(input);
             }
         }
+        return true;
+    },
+    evaluateExistsUnless: function (template, input) {
+        var existsUnless = template.existsUnless;
+        if (existsUnless) {
+            if (Array.isArray(existsUnless)) {
+                return existsUnless.every(function (ew) {
+                    return ew(input);
+                });
+            } else {
+                return existsUnless(input);
+            }
+        }
+        return false;
+    },
+    run: function (template, input) {
+        if (!this.evaluateExistsWhen(template, input)) {
+            return null;
+        }
+        if (this.evaluateExistsUnless(template, input)) {
+            return null;
+        }
         if ((input !== null) && (input !== undefined) && template.dataKey) {
             input = this.evaluateDataKey(input, template.dataKey);
         }

test/test-examples.js

@@ -496,6 +496,98 @@ describe('examples', function () {
         expect(r2.dest_b).to.equal('value_b');
     });
 
+    it('existsUnless - 0', function () {
+        var _ = require('lodash');
+
+        var template = {
+            content: {
+                dest_a: {
+                    dataKey: 'a'
+                },
+                dest_b: {
+                    dataKey: 'b',
+                    existsUnless: _.partialRight(_.has, 'c')
+                },
+            },
+            existsUnless: function (input) {
+                return input && input.private;
+            }
+        };
+
+        var r0 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b',
+            c: 0,
+            private: false
+        });
+        //console.log(r0.dest_a); // 'value_a'
+        //console.log(r0.dest_b); // undefined
+        expect(r0.dest_a).to.equal('value_a');
+        expect(r0.dest_b).to.equal(undefined);
+
+        var r1 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b'
+        });
+        //console.log(r1.dest_a); // 'value_a'
+        //console.log(r1.dest_b); // 'value_b'
+        expect(r1.dest_a).to.equal('value_a');
+        expect(r1.dest_b).to.equal('value_b');
+
+        var r2 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b',
+            private: true
+        });
+        //console.log(r2); // null
+        expect(r2).to.equal(null);
+    });
+
+    it('existsUnless - 1', function () {
+        var _ = require('lodash');
+
+        var template = {
+            content: {
+                dest_a: {
+                    dataKey: 'a'
+                },
+                dest_b: {
+                    dataKey: 'b'
+                },
+            },
+            existsUnless: [_.partialRight(_.has, 'c'), _.partialRight(_.has, 'd')]
+        };
+
+        var r0 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b',
+            c: 'available'
+        });
+        //console.log(r0.dest_a); // 'value_a'
+        //console.log(r0.dest_b); // 'value_b'
+        expect(r0.dest_a).to.equal('value_a');
+        expect(r0.dest_b).to.equal('value_b');
+
+        var r1 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b',
+            d: 'available'
+        });
+        //console.log(r1.dest_a); // 'value_a'
+        //console.log(r1.dest_b); // 'value_b'
+        expect(r1.dest_a).to.equal('value_a');
+        expect(r1.dest_b).to.equal('value_b');
+
+        var r2 = j2j.run(template, {
+            a: 'value_a',
+            b: 'value_b',
+            c: 'available',
+            d: 'available'
+        });
+        //console.log(r2); // null
+        expect(r2).to.equal(null);
+    });
+
     it('dataTransform - 0', function () {
         var nameTemplate = {
             content: {