Compose

README.md

@@ -3,17 +3,24 @@
 This is an implementation of [JSON Pointer](http://tools.ietf.org/html/draft-ietf-appsawg-json-pointer-08).
 
 ## Usage
-
-    var jsonpointer = require("jsonpointer");
-    var obj = { foo: 1, bar: { baz: 2}, qux: [3, 4, 5]};
-    var one = jsonpointer.get(obj, "/foo");
-    var two = jsonpointer.get(obj, "/bar/baz");
-    var three = jsonpointer.get(obj, "/qux/0");
-    var four = jsonpointer.get(obj, "/qux/1");
-    var five = jsonpointer.get(obj, "/qux/2");
-    var notfound = jsonpointer.get(obj, "/quo"); // returns null
-
-    jsonpointer.set(obj, "/foo", 6); // obj.foo = 6;
+```javascript
+var jsonpointer = require('jsonpointer');
+var obj = { foo: 1, bar: { baz: 2}, qux: [3, 4, 5]};
+
+jsonpointer.get(obj, '/foo');     // returns 1
+jsonpointer.get(obj, '/bar/baz'); // returns 2
+jsonpointer.get(obj, '/qux/0');   // returns 3
+jsonpointer.get(obj, '/qux/1');   // returns 4
+jsonpointer.get(obj, '/qux/2');   // returns 5
+jsonpointer.get(obj, '/quo');     // returns null
+
+jsonpointer.set(obj, '/foo', 6);  // sets obj.foo = 6;
+jsonpointer.set(obj, '/qux/-', 6) // sets obj.qux = [3, 4, 5, 6]
+
+pointer = jsonpointer.compile('/foo')
+pointer.get(obj)    // returns 1
+pointer.set(obj, 1) // sets obj.foo = 1
+```
 
 ## Testing
 

jsonpointer.js

@@ -65,6 +65,11 @@ var compilePointer = function (pointer) {
   if (!(pointer instanceof Array)) {
     pointer = pointer.split('/')
     if (pointer.shift() !== '') throw new Error('Invalid JSON pointer.')
+  } else {
+    // Clone the pointer array
+    var newPointer = []
+    for (var i = 0; i < pointer.length; i++) newPointer[i] = pointer[i]
+    pointer = newPointer
   }
 
   return pointer
@@ -94,5 +99,18 @@ var set = function (obj, pointer, value) {
   return traverse(obj, pointer, value)
 }
 
+var compile = function (pointer) {
+  var compiled = compilePointer(pointer)
+  return {
+    get: function (object) {
+      return get(object, compiled)
+    },
+    set: function (object, value) {
+      return set(object, compiled, value)
+    }
+  }
+}
+
 exports.get = get
 exports.set = set
+exports.compile = compile

test.js

@@ -105,4 +105,12 @@ assert.equal(jsonpointer.get(example, '/k\'l'), 6)
 assert.equal(jsonpointer.get(example, '/ '), 7)
 assert.equal(jsonpointer.get(example, '/m~0n'), 8)
 
+// jsonpointer.compile(path)
+var a = {foo: 'bar'}
+var pointer = jsonpointer.compile('/foo')
+assert.equal(pointer.get(a), 'bar')
+assert.equal(pointer.set(a, 'test'), 'bar')
+assert.equal(pointer.get(a), 'test')
+assert.deepEqual(a, {foo: 'test'})
+
 console.log('All tests pass.')