add: proxy object sample js

Author: thutasann

standalone-apis/pure-nodejs-concepts/concepts/README.md

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+# Nodejs + Javascript Concepts

standalone-apis/pure-nodejs-concepts/concepts/proxy/sample-one.js

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+// @ts-check
+const target = {
+	message: 'Hello, World!',
+};
+
+const handler = {
+	get(target, prop, receiver) {
+		console.log(`Getting ${prop}\n`);
+		return prop in target ? target[prop] : `Prop ${prop} does not exist`;
+	},
+	set(target, prop, value) {
+		console.log(`Setting ${prop} to ${value}\n`);
+		target[prop] = value;
+		return true;
+	},
+};
+
+const proxy = new Proxy(target, handler);
+
+console.log('initial message -> ', proxy.message, '\n');
+proxy.message = 'Hello, Proxy';
+console.log('proxy.message --> ', proxy.message);