Initial Commit

async-await/0_callbacks.js

@@ -0,0 +1,45 @@
+// https://javascript.info/callbacks
+
+entryPoint();
+
+function entryPoint () {
+  
+    execute_action('something', function (error, time_of_completion) {
+      if (error) {
+        console.log('Something happened');
+      } else {
+        console.log('Time of completion: ' + new Date(time_of_completion).toDateString());
+      }
+    });
+    console.log("I don't need execute_action's value");
+  }
+
+  function execute_action (param, callback) {
+    if (param == 'something') {
+      console.log('Executing action: ' + param);
+      callback(null, Date.now());
+    } else {
+      // We can call callback with one argument even if
+      // the signature states two parameters.
+      callback(new Error('Invalid parameter'));
+    }
+  }
+
+  /*
+    This is useful when, for example, execute_action performs slow operations
+    (such as I/O, HTTP requests etc) and we need its result to continue a
+    specific operation (in this case the date of completion), without blocking
+    other portions of code that do not need such value, in this case
+    "console.log("I don't need execute_action's value");"
+
+    But please note that this is only an example. In this code all
+    operations will be executed synchronously, but this allows us
+    to understand the basics of this mechanism.
+
+    Output:
+        Executing action: something
+        Time of completion: Sun Jun 30 2024
+        I don't need execute_action's value
+    
+  */
+