add util.ts for sharing common functions between frontend and backend

src/util.js

@@ -0,0 +1,24 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.debug = exports.ucfirst = exports.sleep = exports.PENDING = exports.UP = exports.DOWN = void 0;
+exports.DOWN = 0;
+exports.UP = 1;
+exports.PENDING = 2;
+function sleep(ms) {
+    return new Promise(resolve => setTimeout(resolve, ms));
+}
+exports.sleep = sleep;
+function ucfirst(str) {
+    if (!str) {
+        return str;
+    }
+    const firstLetter = str.substr(0, 1);
+    return firstLetter.toUpperCase() + str.substr(1);
+}
+exports.ucfirst = ucfirst;
+function debug(msg) {
+    if (process.env.NODE_ENV === "development") {
+        console.log(msg);
+    }
+}
+exports.debug = debug;