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For this example it is recommended that you have the latest most stable release of Node.js + npm installed.
Now you will need express to run a simple server. (more…)

Using a subject to create an observable is the recommended method of inter-component communication by the official angular documentation.
The following code was tested with Angular 5.2.2. (more…)

The following is the fastest way to integrate Google Analytics with your self hosted WordPress website without using any external applications or plugins. By injecting plain javascript into your tag, you won’t have to worry about incurring the overhead of adding a new plugin to your site for a small 2 line code addition. (more…)

You can login as the user you want to delete history from and then use the following command. For example if you want to delete from root

sudo -i
cat /dev/null > ~/.bash_history && history -c && exit

sudo crontab -e

The following cronjobs will run every hour. Make sure you replace the database connection string values (make sure you have the right privileges on the database being used.) and backup folder paths with the appropriate ones.

0 * * * * cd /cron/backup && tar -zcvf backup.tar.gz /var/www/html/
0 * * * *  mysqldump -u user_name -p'password' db_name> /cron/backup/backup.sql

Now save the changes and restart the cron service.

Ctrl+O
Enter
Ctrl+X
sudo service cron restart

This php script repairs and optimizes all the tables in the selected database. Make sure you provide the right values in the connection string.

Script

optimize.php

 $tablename)
   {
       if(mysqli_query($link,"REPAIR TABLE `$tablename`")) 
           { 
           echo '\nRepair Success: '.$tablename;
            }
       else 
         die(mysqli_error($link));
       if(mysqli_query($link,"OPTIMIZE TABLE `$tablename`")) 
          { 
           echo '\nOptmize Success: '.$tablename;
          }
       else
          die(mysqli_error($link));
   }
}

mysqli_close($link);

Cronjob

crontab -e
0 * * * * php /var/www/html/optimize.php
Ctrl+O
Enter
Ctrl+X
sudo service cron restart

I am using MariaDB 5.x for this post. However this should work on most recent MySQL databases.
Make sure that MySQL server is running and login with the root or with the user that has privileges of creating events on the database you would like to use.

mysql -u root -p password123 db_name
SET GLOBAL event_scheduler = ON;

(or)

mysql -u root -p
SET GLOBAL event_scheduler = ON;
use db_name;

CREATE EVENT e_hourly
    ON SCHEDULE
      EVERY 1 HOUR
    COMMENT 'Clears out not active users after 24 hours of link being sent.'
    DO
      DELETE FROM Users_table WHERE activated='n' AND DATEDIFF( NOW(),  time ) >1;

The above statement will create an event that runs every hour starting from the moment you execute this script. But if you want it to start executing at some other time (ex: January 30th 2018 at 00:00), then you can use the START command in the following way.

CREATE EVENT 
  ON SCHEDULE 
    EVERY 1 DAY
      STARTS '2018-01-30 00:00:00'
    COMMENT 'Clears out not active users after 24 hours of link being sent.'
DO
DELETE FROM Users_table_message WHERE activated='n' AND DATEDIFF( NOW(),  time ) >1;

SHOW EVENTS;

Cronjobs using Crontab

This can also be done directly using crontab and scheduling a cronjob. Consider the following code for example.

crontab -e

This will usually open crontab file with the nano editor.

#!/bin/bash
mysql --user=root --password=password123 --database=db_name --execute="DELETE FROM Users_table WHERE activated='n' AND DATEDIFF( NOW(),  time ) >1"

Now to save the changes to disk and exit while using the nano editor, use the following commands.

Ctrl+O
Enter
Ctrl+X

Scripts

You can also use php scripts to run the mysql query. For example the following script runs every hour.

0 * * * * /usr/local/bin/php /var/www/html/clean_mysql_script.php

Make sure you are logged into the WordPress admin console and that you have necessary permissions to toggle the Jetpack modules and navigate to the following link after replacing the domain name with yours. Here you should be able to easily activate and deactivate the Jetpack list of modules easily.
https://www.url-here.com/wp-admin/admin.php?page=jetpack_modules

Write a function to determine whether a person can reach the other end of the array if he starts at index 0 and if he cannot hop more than the value contained at that index.

var jumper = [];
var arr = [4, 0, 0, 1];

function hopper(index) {
  if (index + arr[index] >= arr.length) {
    jumper[index] = true;
    return;
  } else {
    for (var i = index + 1; i <= index + arr[index]; i++) {
      if (jumper[i]) {
        jumper[index] = true;
        return;
      }
    }
    jumper[index] = false;
  }
}

function isReachable() {
  for (var j = arr.length - 1; j >= 0; j--) {
    hopper(j);
  }
  return jumper[0];
}

isReachable()

Output

isReachable => true
jumper => [true, false, false, true]

Time Complexity: O(n^2)
Space Complexity: O(n)
Demo

Get Minimum Hops

To get the minimum hops, now we need to keep track of the hops at each index using another array or we can create a Data Structure (here Object) to keep track of them.

var jumper = [];
var mjumper = [];
var arr = [4, 1, 1, 1];

function hopper(index) {
  if (index + arr[index] >= arr.length) {
    jumper[index] = true;
    mjumper[index] = 1;
  } else {
    for (var i = index + 1; i <= index + arr[index]; i++) {
      if (jumper[i]) {
        if (jumper[index]) {
          mjumper[index] = Math.min(mjumper[i] + 1, mjumper[index]);
        } else {
          jumper[index] = true;
          mjumper[index] = mjumper[i] + 1;
        }
      }
    }
    if (!jumper[index]) {
      jumper[index] = false;
    }
  }
}

function getMinimumSteps() {
  for (var j = arr.length - 1; j >= 0; j--) {
    hopper(j);
  }

  if (jumper[0])
    return mjumper[0];
  else return -1;
}

getMinimumSteps();

Output

1

Time Complexity: O(n^2)
Space Complexity: O(n)
Demo

SimpleJS is a lightweight javascript library to get you started on plane javascript project that doesn’t need libraries to start with.
Some of the major functionality includes the following.

• Manipulate Cookies.
• Make GET, POST calls with JSON data.
• Load attributes to an element by passing an object.
• Insert element before an element in DOM.
• Get Parent element in DOM.