added check if valid address to docs (#440)

* added check if valid address to docs

* Update package.json

docs/examples/keyring/03_validate_address/README.md

@@ -0,0 +1,5 @@
+# Validate Adress
+
+- This function will return true if the address is a legitamate Polkadot address and false if it is not
+
+- Works both with Ed25519 and Sr25519 key types

docs/examples/keyring/03_validate_address/index.js

@@ -0,0 +1,16 @@
+const { encodeAddress, decodeAddress } = require('@polkadot/keyring');
+const { isHex, hexToU8a } = require('@polkadot/util');
+
+const address = '5GrpknVvGGrGH3EFuURXeMrWHvbpj3VfER1oX5jFtuGbfzCE';
+
+const isValidAddressPolkadotAddress = () => {
+  try {
+    encodeAddress(isHex(address) ? hexToU8a(address) : decodeAddress(address));
+    return true;
+  } catch (error) {
+    return false;
+  }
+};
+
+const isValid = isValidAddressPolkadotAddress();
+console.log(isValid);

docs/examples/keyring/03_validate_address/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "03_validate_address",
+  "version": "0.1.0",
+  "description": "Example showing how to validate a polkadot address",
+  "main": "index.js",
+  "author": "Jesse",
+  "license": "MIT",
+  "scripts": {
+    "clean": "rimraf node_modules",
+    "start": "node index.js"
+  },
+  "dependencies": {
+    "@polkadot/keyring": "*"
+  },
+  "devDependencies": {
+    "rimraf": "^2.6.2"
+  }
+}