Summer: January 2026

Thursday, 15 January 2026

SFTP server

#log in
sftp leo@82.992.123.124

#after log in

# upload a file:
put test.txt

# download a file
get test.txt

# delete a file
rm test.txt

Directly copy file between the server and the local machine if can ssh to the server

# find server public ip: 100.31.47.111

# ssh to the server
ssh -i /Users/leo/path/noc.pem ec2-user@100.31.47.111

# copy file to server
scp -i /Users/leo/path/noc.pem /Users/leo/path/test.txt.gpg  ec2-user@100.31.47.111:/home/ec2-user/

# copy file from server to local
scp -i /Users/leo/path/noc.pem  ec2-user@100.31.47.111:/home/ec2-user/test.txt  /Users/leo/path/

Decrypt gpg file

# verify have the private key
gpg --list-secret-keys

# decrypt. when prompt, provide private key phrase
gpg --decrypt --output mytest.csv  mytest.csv.gpg

Monday, 12 January 2026

CORS

Error: Access to fetch at .... has been blocked by CORS

CORS stands for cross origin resource share. If use Javascript to fetch a endpoint and endpoin is not the same origin as the current page, may see the above error. Here origin is protocol + domain + port.

//host is https://examplea.com
<script>

 let endpoint = "https://exampleb.com/create-order";
 return fetch(endpoint, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(data)
    })
      .then(resp => {
        if (!resp.ok) throw new Error('Network response was not ok');
        return resp.json();
      });
</script>

To solve the issue. For that end point of exampleb.com. the response needs to set headers such as

$response = $response->withHeader('Access-Control-Allow-Origin', "*");
        
return $response->withHeader('Access-Control-Allow-Headers', 'X-Requested-With,x-api-key, Content-Type, Accept, Origin, Authorization, X-Authorization-JWT, X-CSRF-Token')
	->withHeader('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
    }

Wednesday, 7 January 2026

Javascript Class

Class in ECMAScript 5

function PersonType(name) {
    this.name = name;
}

PersonType.prototype.sayName = function() {
    console.log("your name:" + this.name);
}

let person = new PersonType("leo");
person.sayName();

Class in ECMAScript 6

class PersonType {
    constructor(name) {
        this.name = name;
    }
    sayName() {
        console.log("your name:" + this.name);
    }
}

let person = new PersonType("leo");
person.sayName();

Use class in web page

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <script src="person.js"></script>
    <script>
        let p = new Person('leo');
        p.sayName();
    </script>
</head>
</html>

person.js

class Person {
    constructor(name) {
        this.name = name;
    }
    sayName() {
        console.log("your name:" + this.name);
    }
}

// export to global namespace so index.html can see it
window.Person = Person;

Javascript Promise

Create a promise and consume a promise

example one

let p = new Promise((resolve, reject) => {
    let n = Math.floor(Math.random() * 100);
    let good = n % 2 == 0 ? true : false;

    if (good) {
        setTimeout(resolve, 100, { "dd": 1212 });
    } else {
        setTimeout(reject, 200, "bad2");
    }
});

p.then((v) => console.log("suc", v))
    .catch((v) => console.log("failed:", v));

//this is identical as the above
p.then((v) => console.log("suc", v), (v) => console.log("failed:", v));

example two

import { readFile as _readFile } from 'fs';

let p = new Promise((resolve, reject) => {
  _readFile("./test.js", 'utf8', (err, data) => {
    if (err) {
      reject(err);
    } else {
      resolve(data);
    }
  })
});

p.then((data) => console.log("good", data))
  .catch((err) => console.log("err", err))

Use await to consume a function which return a promise

example one

function myCreate() {
    return new Promise((resolve, reject) => {
        let n = Math.floor(Math.random() * 100);
        let good = n % 2 == 0 ? true : false;

        if (good) {
            setTimeout(resolve, 100, { "dd": 1212 });
        } else {
            setTimeout(reject, 200, "bad2");
        }
    });
}

try {
    const ans = await myCreate();
    console.log("ans", ans);
} catch (err) {
    console.log("err:", err);
}

use async function to consume the promise

function myCreate() {
    return new Promise((resolve, reject) => {
        let n = Math.floor(Math.random() * 100);
        let good = n % 2 == 0 ? true : false;

        if (good) {
            setTimeout(resolve, 100, { "dd": 1212 });
        } else {
            setTimeout(reject, 200, "bad2");
        }
    });
}

async function test() {
    try {
        const ans = await myCreate();
        console.log("ans", ans);
    } catch (err) {
        console.log("err:", err);
    }
}

test();

You still can use then to consume a promise returned by a function.

function myCreate() {
    return new Promise((resolve, reject) => {
        let n = Math.floor(Math.random() * 100);
        let good = n % 2 == 0 ? true : false;

        if (good) {
            setTimeout(resolve, 100, { "dd": 1212 });
        } else {
            setTimeout(reject, 200, "bad2");
        }
    });
}

myCreate().then((ans) => console.log("ans", ans), (err) => console.log("err:", err));

Tuesday, 6 January 2026

Install older version vscode

Install

go to vscode versions
Pick a one and download
For mac, unzip the file. Drag app file into Application folder

Prevent from upgrading automatically

– Open VS Code.
– Press ⌘, (Command-Comma) to open Settings.
– In the search box type “update”.
– Under Features → Updates find “Update: Mode” and set it to “none”.

Summer