Node

Author: prabaprakash

Advance Nodejs/1. nextTick.js

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+function hideString(str, done) {
+    process.nextTick(()=>{
+     done(str);
+    });
+}
+
+hideString("hello world", (hidden)=>{
+    console.log(hidden);
+})
+
+console.log('end');

Advance Nodejs/2. delay.js

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+function delay(seconds, callback) {
+    setTimeout(callback, seconds*1000);
+}
+
+delay(2, () => {
+    console.log('two seconds');
+    delay(1, () => {
+        console.log('three seconds');
+        delay(1, () => {
+        console.log('four seconds');
+        });
+    })
+})

Advance Nodejs/3. Promise.js

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+var delay = (seconds) => new Promise((resolves, rejects)=> {
+    setTimeout(resolves('the long delay has ended'), seconds*1000);
+ });
+
+delay(1).then(console.log)
+        .then(()=> 42)
+        .then((number)=> console.log(`hello world - ${number}`))
+
+console.log('end first tick');

Advance Nodejs/4. Promise Error.js

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+var delay = (seconds) => new Promise((resolves, rejects)=> {
+        throw new Error('argh');
+        setTimeout(resolves('the long delay has ended'), seconds*1000);
+ });
+
+delay(1).then(console.log)
+        .then(()=> 42)
+        .then((number)=> console.log(`hello world - ${number}`))
+        .catch((error)=>console.log(`Error: ${error.message}`))
+
+console.log('end first tick');

Advance Nodejs/5. Promise Rejects.js

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+var delay = (seconds) => new Promise((resolves, rejects)=> {
+        if(seconds > 3) {
+                rejects(new Error(`${seconds} is too long`));
+        }
+        throw new Error('argh');
+        setTimeout(resolves('the long delay has ended'), seconds*1000);
+ });
+
+delay(4).then(console.log)
+        .then(()=> 42)
+        .then((number)=> console.log(`hello world - ${number}`))
+        .catch((error)=>console.log(`Error: ${error.message}`))
+
+console.log('end first tick');

Advance Nodejs/6. promisify.js

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+var { promisify } = require('util');
+
+var delay = (seconds, callback) => {
+    if(seconds > 3) {
+        callback(new Error('${seconds} seconds it too long!'));
+    }
+    else {
+        setTimeout(()=> callback(null, `the ${seconds} seconds delay is over`),
+        seconds
+        );
+    }
+}
+
+var promisifyDelay = promisify(delay);
+
+promisifyDelay(5)
+     .then(console.log)
+     .catch((error) => console.log(`error: ${error.message}`));

Advance Nodejs/7. Promise.race.js

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+var fs = require('fs');
+var { promisify } = require('util');
+var writeFile = promisify(fs.writeFile);
+var unlink = promisify(fs.unlink);
+var readdir = promisify(fs.readdir);
+var beep = () => process.stdout.write("\x07");
+var delay = (seconds) => new Promise((resolves) => {
+    setTimeout(resolves, seconds*1000);
+})
+
+Promise.race([
+  delay(5),
+  delay(2),
+  delay(3),
+  delay(5)
+]).then(() => readdir(__dirname))
+  .then(console.log);

Advance Nodejs/8. Promice.Sequentially.js

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+var fs = require('fs');
+var { promisify } = require('util');
+var writeFile = promisify(fs.writeFile);
+var unlink = promisify(fs.unlink);
+var beep = () => process.stdout.write("\x07");
+var delay = (seconds) => new Promise((resolves) => {
+    setTimeout(resolves, seconds*1000);
+})
+
+const doStuffSequentially = () => Promise.resolve()
+  .then(() => console.log('starting'))
+  .then(() => delay(1))
+  .then(() => 'waiting')
+  .then(console.log)
+  .then(() => delay(2))
+  .then(() => writeFile('file.txt', 'Sample File...'))
+  .then(beep)
+  .then(() => 'file.txt created')
+  .then(console.log)
+  .then(() => delay(3))
+  .then(() => unlink('file.txt'))
+  .then(beep)
+  .then(() => 'file.txt removed')
+  .then(console.log)
+  .catch(console.error);
+
+doStuffSequentially()
+  .then(() => console.log('again again!!!'))
+  .then(() => doStuffSequentially())
+  .then(() => console.log('enough already...'));