fix: implement JSON so roundtrip works as expected

This commit adds a test case, and simply reuses the
the `toString` implementation.

Author: Chris Anderson

src/index.js

@@ -56,6 +56,16 @@ Multiaddr.prototype.toString = function toString () {
   return codec.bufferToString(this.buffer)
 }
 
+/**
+ * Returns Multiaddr as a JSON encoded object
+ *
+ * @returns {String}
+ * @example
+ * JSON.stringify(Multiaddr('/ip4/127.0.0.1/tcp/4001'))
+ * // '/ip4/127.0.0.1/tcp/4001'
+ */
+Multiaddr.prototype.toJSON = Multiaddr.prototype.toString;
+
 /**
  * Returns Multiaddr as a convinient options object to be used with net.createConnection
  *

test/index.spec.js

@@ -36,6 +36,11 @@ describe('construction', () => {
     expect(multiaddr(udpAddr).buffer).to.deep.equal(udpAddr.buffer)
   })
 
+  it('reconstruct with JSON', () => {
+    expect(multiaddr(JSON.parse(JSON.stringify(udpAddr))).buffer === udpAddr.buffer).to.equal(false)
+    expect(multiaddr(JSON.parse(JSON.stringify(udpAddr))).buffer).to.deep.equal(udpAddr.buffer)
+  })
+
   it('empty construct still works', () => {
     expect(multiaddr('').toString()).to.equal('/')
   })