feat: add isMultiaddr method

Author: dignifiedquire

README.md

@@ -191,6 +191,12 @@ const printerOverProxy = proxy.encapsulate(printer)
 // <Multiaddr /ip4/10.20.30.40/tcp/443/ip4/192.168.0.13/tcp/80>
 ```
 
+### Misc
+
+#### `multiaddr.isMultiaddr(addr)`
+
+Returns `true` if the passed in `addr` is a valid `multiaddr`.
+
 ## Installation
 
 ### npm

src/index.js

@@ -166,3 +166,14 @@ Multiaddr.prototype.fromStupidString = function fromStupidString (str) {
 
 // patch this in
 Multiaddr.protocols = protocols
+
+Multiaddr.isMultiaddr = function isMultiaddr (addr) {
+  if (addr.constructor && addr.constructor.name) {
+    return addr.constructor.name === 'Multiaddr'
+  }
+
+  return Boolean(
+    addr.fromStupidString &&
+    addr.protos
+  )
+}

test/index.spec.js

@@ -1,3 +1,4 @@
+/* eslint max-nested-callbacks: ["error", 8] */
 /* eslint-env mocha */
 'use strict'
 
@@ -515,4 +516,14 @@ describe('helpers', () => {
       )
     })
   })
+
+  describe('multiaddr.isMultiaddr', () => {
+    it('handles different inputs', () => {
+      expect(multiaddr.isMultiaddr(multiaddr('/'))).to.be.eql(true)
+      expect(multiaddr.isMultiaddr('/')).to.be.eql(false)
+      expect(multiaddr.isMultiaddr(123)).to.be.eql(false)
+
+      expect(multiaddr.isMultiaddr(Buffer('/hello'))).to.be.eql(false)
+    })
+  })
 })