Added "change" attribute

README.md

@@ -92,7 +92,8 @@ var config = {
       address: "1A2JN4JAUoKCQ5kA4pHhu4qCqma8jZSU81",
       value: 1000
     }]
-  }
+  },
+  change: "1CBtFi158ieej44LJ9XkoGuH99t1BFh15j"
 }
 ```
 
@@ -436,6 +437,32 @@ datapay.build(tx, function(err, tx) {
 })
 ```
 
+
+#### 6. `change`
+
+The `change` attribute is used to optionally specify where change for unspent funds pays out to, making it easy to implement single-use addresses.
+
+- default: sender's address
+
+```
+const tx = {
+  safe: true,
+  data: ["0x6d02", "hello world"],
+  pay: {
+    key: "5JZ4RXH4MoXpaUQMcJHo8DxhZtkf5U5VnYd9zZH8BRKZuAbxZEw",
+  },
+  change: "1CBtFi158ieej44LJ9XkoGuH99t1BFh15j"
+}
+datapay.build(tx, function(err, res) {
+  /**
+  * res contains the generated transaction object
+  * (a signed transaction, since 'key' is included.)
+  * It also pays any unspent change to the address
+  * in the change field instead of returning to sender.
+  **/
+})
+```
+
 ---
 
 ### C. tx

index.js

@@ -62,8 +62,10 @@ var build = function(options, callback) {
           tx.to(receiver.address, receiver.value)
         })
       }
-
-      tx.fee(defaults.fee).change(address);
+
+      //Pay remaining outputs to next address if defined, or default back to sender's address
+      const change = options.change ? new bitcoin.Address.fromString(options.change) : address;
+      tx.fee(defaults.fee).change(change);
       let opt_pay = options.pay || {};
       let myfee = opt_pay.fee || Math.ceil(tx._estimateSize()* (opt_pay.feeb || defaults.feeb));
       tx.fee(myfee);

package.json

@@ -23,7 +23,7 @@
     "mingo": "^2.2.4"
   },
   "peerDependencies": {
-    "bsv": "0.27.1"
+    "bsv": "0.30.0"
   },
   "files": [
     "dist"