Module examples

2018-03-26 15:40:48 -03:00
parent a9ce3b9c5c
commit ed4c76597f
8 changed files with 128 additions and 0 deletions
@@ -0,0 +1,30 @@
+/* @flow */
+
+/*
+    In the following code, the only thing that needs
+    an explicit type declaration for Flow, is "name".
+    Flow can work out on its own the rest of the types.
+*/
+
+const myCounter = ((name: string) => {
+    let count = 0;
+
+    const get = () => count; // private
+
+    const inc = () => ++count;
+
+    const toString = () => `${name}: ${get()}`;
+
+    return {
+        inc,
+        toString
+    };
+})("Clicks");
+
+console.log(myCounter); // an object with "inc" and "toString" properties
+
+myCounter.inc(); // 1
+myCounter.inc(); // 2
+myCounter.inc(); // 3
+
+myCounter.toString(); // "Clicks: 3"
@@ -0,0 +1,19 @@
+/* @flow */
+
+let name: string = "";
+let count: number = 0;
+
+let get = () => count;
+let inc = () => ++count;
+let toString = () => `${name}: ${get()}`;
+
+/*
+    Since we cannot initialize anything otherwise,
+    a common pattern is to provide a "init()" function
+    to do all necessary initializations.
+*/
+const init = (n: string) => {
+    name = n;
+};
+
+export default { inc, toString, init }; // everything else is private
@@ -0,0 +1,28 @@
+/* @flow */
+
+let name: string = "";
+let count: number = 0;
+
+let get = () => count;
+
+let throwNotInit = () => {
+    throw new Error("Not initialized");
+};
+
+let inc = throwNotInit;
+let toString = throwNotInit;
+
+/*
+    Since we cannot initialize anything otherwise,
+    a common pattern is to provide a "init()" function
+    to do all necessary initializations. In this case,
+    "inc()" and "toString()" won't work as expected
+    if the module wasn't initialized.
+*/
+const init = (n: string) => {
+    name = n;
+    inc = () => ++count;
+    toString = () => `${name}: ${get()}`;
+};
+
+export default { inc, toString, init }; // everything else is private
@@ -0,0 +1,16 @@
+/* @flow */
+
+import myCounter from "/home/fkereki/MODERNJS/chapter02/src/module_counter.SIMPLE.js";
+
+/*
+    Initialize the counter appropriately
+*/
+myCounter.init("Clicks");
+
+/*
+    The rest would work as before
+*/
+myCounter.inc(); // 1
+myCounter.inc(); // 2
+myCounter.inc(); // 3
+myCounter.toString(); // "Clicks: 3"
@@ -0,0 +1,15 @@
+// No Flow anywhere!
+
+let name = "";
+let count = 0;
+
+let get = () => count;
+
+let inc = () => ++count;
+let toString = () => `${name}: ${get()}`;
+
+const init = n => {
+    name = n;
+};
+
+export default { inc, toString, init }; // everything else is private
@@ -0,0 +1,20 @@
+<http>
+
+    <head> </head>
+
+    <body>
+        See the console for output.
+
+        <script type="module" src="./module_counter.SIMPLE.js"></script>
+        <script type="module">
+            import myCounter from "./module_counter.SIMPLE.js";
+
+            myCounter.init("Clicks");
+
+            console.log(myCounter.inc()); // 1
+            console.log(myCounter.inc()); // 2
+            console.log(myCounter.inc()); // 3
+            console.log(myCounter.toString()); // "Clicks: 3"
+        </script>
+    </body>
+</http>