Add makeInterfaceId.ERC1820.

README.md

@@ -131,6 +131,9 @@ Same as `inLogs`, but for events emitted in an arbitrary transaction (of hash `t
 #### ERC165
 Calculates the [ERC165](https://eips.ethereum.org/EIPS/eip-165) interface ID of a contract, given a series of function signatures.
 
+#### ERC1820
+Calculates the [ERC1820](https://eips.ethereum.org/EIPS/eip-1820) interface hash of a function, given its signature.
+
 ---
 
 ### send

src/makeInterfaceId.js

@@ -1,8 +1,8 @@
-function ERC165 (interfaces = []) {
+function ERC165 (functionSignatures = []) {
   const INTERFACE_ID_LENGTH = 4;
 
-  const interfaceIdBuffer = interfaces
-    .map(methodSignature => web3.utils.soliditySha3(methodSignature)) // keccak256
+  const interfaceIdBuffer = functionSignatures
+    .map(signature => web3.utils.soliditySha3(signature)) // keccak256
     .map(h =>
       Buffer
         .from(h.substring(2), 'hex')
@@ -18,8 +18,8 @@ function ERC165 (interfaces = []) {
   return `0x${interfaceIdBuffer.toString('hex')}`;
 }
 
-function ERC1820 (inteface) {
-
+function ERC1820 (functionSignature) {
+  return web3.utils.soliditySha3(functionSignature); // keccak256
 }
 
 module.exports = {

test/src/makeInterfaceId.test.js

@@ -18,4 +18,12 @@ describe('makeInterfaceId', function () {
       ])).to.equal(ownableId);
     });
   });
+
+  describe('ERC165', function () {
+    it('calculates the interface id from function signatures', async function () {
+      expect(makeInterfaceId.ERC1820('ERC777Token')).to.equal(
+        '0xac7fbab5f54a3ca8194167523c6753bfeb96a445279294b6125b68cce2177054'
+      );
+    });
+  });
 });