new class js -advanced

02_advanced/MATERIAL/advanced-js/lesson_03/examples/promise_4.js

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+const tryWork = (resolve, reject) => {
+  const ergebnis = 21 * 2;
+  if (Math.random() < 0.5) {
+    resolve(ergebnis);
+  } else {
+    reject('nope');
+  }
+};
+
+const p4 = new Promise(tryWork);
+
+p4.then(
+  (result) => console.log('OK: ' + result),
+  (reason) => console.log('KO: ' + reason)
+);

02_advanced/MATERIAL/advanced-js/lesson_03/examples/promise_stack_trace.js

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+const tryWork = (resolve, reject) => {
+  const ergebnis = 21 * 2;
+  if (Math.random() < 0.5) {
+    resolve(ergebnis);
+  } else {
+    reject(new Error('nope'));
+  }
+};
+
+new Promise(tryWork)
+  .then(() => new Promise(tryWork))
+  .then(() => new Promise(tryWork))
+  .then((result) => console.log('OK: ' + result))
+  .catch((err) => {
+    console.log('KO: ' + err.message);
+    console.log(err.stack);
+  });

02_advanced/MATERIAL/advanced-js/lesson_03/examples/promise_wait.js

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+const wait = () => new Promise((resolve) => setTimeout(resolve, 1000));
+
+wait()
+  .then(() => {
+    console.log('The');
+    return wait();
+  })
+  .then(() => {
+    console.log('pyramid');
+    return wait();
+  });
+// etc...

02_advanced/MATERIAL/advanced-js/lesson_03/examples/pyramid_of_doom.js

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+// print a phrase, a word at a time:
+// the pyramid of doom appears
+
+setTimeout(() => {
+  console.log('The');
+
+  setTimeout(() => {
+    console.log('pyramid');
+
+    setTimeout(() => {
+      console.log('of');
+
+      setTimeout(() => {
+        console.log('doom');
+
+        setTimeout(() => {
+          console.log('keeps');
+
+          setTimeout(() => {
+            console.log('growing.');
+          }, 1000);
+        }, 1000);
+      }, 1000);
+    }, 1000);
+  }, 1000);
+}, 1000);

02_advanced/MATERIAL/advanced-js/lesson_03/examples/pyramid_of_doom_avoided.js

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+// print a phrase, a word at a time:
+// use promises to avoid the pyramid of doom
+
+const printDelay = (time, str) =>
+  new Promise((resolve) =>
+    setTimeout(() => {
+      console.log(str);
+      resolve();
+    }, time)
+  );
+
+printDelay(1000, 'The')
+  .then(() => printDelay(1000, 'pyramid'))
+  .then(() => printDelay(1000, 'of'))
+  .then(() => printDelay(1000, 'doom'))
+  .then(() => printDelay(1000, 'is'))
+  .then(() => printDelay(1000, 'defeated.'));

02_advanced/MATERIAL/advanced-js/lesson_03/examples/read_file_async.js

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+const fs = require('fs');
+
+fs.readFile('data/file.txt', 'UTF8', (error, content) => {
+  if (error) {
+    console.log('could not read file');
+  } else {
+    console.log(content);
+  }
+});

02_advanced/MATERIAL/advanced-js/lesson_03/examples/read_file_promise.js

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+const fs = require('fs');
+
+const getFileContent = (path, encoding = 'utf-8') => {
+  return new Promise((resolve, reject) => {
+    fs.readFile(path, encoding, (error, data) => {
+      if (error) {
+        reject(error);
+      } else {
+        resolve(data);
+      }
+    });
+  });
+};
+
+getFileContent('data/file.txt')
+  .then((data) => console.log(data))
+  .catch((err) => console.error(`Something went wrong: ${err}`));

02_advanced/MATERIAL/advanced-js/lesson_03/examples/read_file_promises.js

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+const fs = require('fs');
+
+const getFileContent = (path, encoding = 'utf-8') => {
+  return fs.promises.readFile(path, encoding);
+};
+
+getFileContent('data/file.txt')
+  .then((data) => console.log(data))
+  .catch((err) => console.error(`Something went wrong: ${err}`));

02_advanced/MATERIAL/advanced-js/lesson_03/examples/read_file_util_promisify.js

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+const fs = require('fs');
+const util = require('util');
+
+const getFileContent = util.promisify(fs.readFile);
+
+getFileContent('data/file.txt', 'UTF8')
+  .then((data) => console.log(data))
+  .catch((err) => console.error(`Something went wrong: ${err}`));