Coding in JavaScript is one of the critical skills required in building websites. Though mastering JavaScript is a journey to the center of the earth, continuous learning will help you make it.

We have seen some of the JavaScript functions like find(), forEach() earlier. Now, let’s learn about the function includes() in JavaScript.

<script>

inputArray = ['Create', 'Read', 'Update', 'Delete', 'Filter'];

inputArray.includes('Read'); //returns true

inputArray.includes('Read','3'); //returns false

inputArray.includes('Error'); //returns false

inputArray.includes('Delete','-1'); //returns false inputString = 'How to learn JavaScript?';

inputString.includes('learn'); //returns true

inputString.includes('learn','8'); //returns false

</script> 

About JavaScript includes

It checks if an array or string includes a given value.

In an array context, it checks the given value is one among the array elements. In the string prototype, the includes() in JavaScript checks if the given value is the substring.

Syntax, parameters and return value

includes(searchElement, [fromIndex]); 

It has two parameters, searchElement and fromIndex. The fromIndex is optional and its default value is 0 to start with.

The fromIndex accepts signed numbers. With a negative value, it applies this formula to compute the position to start.

fromIndex = arrayLength + signedFromIndex


It returns boolean true if any match is found or false otherwise.

Note:

• JavaScript includes() searches array or string with case sensitivity.
• It can also be called as a generic method.
• It works in most modern browsers.
• The negative value is not applicable for the includes() in the String prototype.
• The Array.prototype.includes() will not search for a sub-array.

Where to use JavaScript includes

The includes in JavaScript can be used for many scenarios. Some of them are listed below.

1. To form a conditional code block based on the presence of the search element in an array or string.
2. To highlight the keyword in the search result, if the includes in JavaScript returns true.
3. To make the select, checkbox, radio options selected if the options found in the haystack.

Visit the linked article to know the other array prototype methods in JavaScript.

Examples for using includes in JavaScript

This article includes 4 examples to see how to use JavaScript includes(). Those are,

1. To search array if a specified element exists or not.
2. To use includes with a positive or negative fromIndex parameter.
3. To use String.prototype.includes.
4. To invoke includes() as a generic method.

Search array element using Includes in JavaScript

This example contains an array of 4 strings. It defines a custom function checkOption() to form a condition using includes().

This function receives a string and applies array.includes() on it. It returns Boolean true if the passed element is found on the array.

It prepares the output string based on the boolean value returned. It writes the log on the console to see the result of the program.

how-to-use-includes-in-javascript-array.php

<script> var optionArray = [ 'Create', 'Read', 'Update', 'Delete' ]; checkOption('Read'); checkOption('Filter'); function checkOption(keyword) { var isIncludes = optionArray.includes(keyword); if(!isIncludes) { console.log(keyword + ": not exists"); } else { console.log(keyword + ": exists"); } }

</script> 

Includes function with optional from-index parameter

It uses the optional fromIndex parameter while calling the includes() in JavaScript.

It supplies either positive or negative values in the second parameter. On getting a negative index, it computes the position from where it should start the search.

As passed -1 the computed position is 5, since arrayLength+negativeIndex = 6+(-1) = 5.

From the 5th position, it searches for ‘Pagination’ and returns true. When it searches for ‘Filter’ then it will return false.

javascript-includes-with-from-index.php

<script>

var optionArray = [ 'Create', 'Read', 'Update', 'Delete', 'Filter', 'Pagination' ]; console.log(optionArray.includes('Update', 2));

console.log(optionArray.includes('Update', 3));

console.log(optionArray.includes('Pagination', -1));

console.log(optionArray.includes('Filter',-1));

</script> 

JavaScript string includes

It’s for using String.prototype.includes() in Javascript. It assigns a long string to a variable and searches the passed keyword on it.

It also receives fromIndex position. A negative index will create no change. This program uses the fromIndex default value 0 and searches the string end to end.

check-string-includes-substring.php

<script>

var inputString = "How much wood would a woodchuck chuck if a woodchuck could chuck wood?";

var result = inputString.includes("woodchuck");

console.log(result);

</script> 

Invoke includes in JavaScript on array-like objects

JavaScript allows calling the includes() function as a generic method. In the above examples, the includes() is called with respect to this value representing an array or string context.

This example calls the includes in JavaScript on a functions’ argument list instead of an array.

how-to-call-includes-as-generic.php

<script>

(function() { console.log(Array.prototype.includes.call(arguments, 'Read', 1)); console.log(Array.prototype.includes.call(arguments, 'Read', -1));

})('Create', 'Read', 'Update', 'Delete') </script> 

Similar JavaScript methods like includes

There are more functions in JavaScript as like as the includes(). The below list shows some of those functions.

• find() – applies condition on an array and returns the first element satisfying the condition.
• findIndex() – as like as find() but returns index instead of the value.
• indexOf() – returns index by element value.
• lastIndexOf() – returns last index of an input element. It makes difference if the there are multiple occurances of the passed element.

Conclusion

We have seen about the includes in JavaScript end to end. The above article contains the basic idea about this function. It covers a beginner’s level introductory section and the usage mechanisms.

The examples will make it clear how to use includes in JavaScript. I hope the scenarios to use and the list of related functions gives relevancy to get the idea.

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You want to plot a series of data with unique styles. You need to pick various line styles from a list but not sure how to get started. This tutorial will help you out.

Yes, there is a list of line styles in matplotlib. To get the list, import the lines from the matplotlib library.

from matplotlib import lines

Next, get the keys from the lineStyle attribute.

lines.lineStyles.keys()

You can then print the styles and choose your preferred style per plot.

print(lines.lineStyles.keys())

The result is

dict_keys(['-', '--', '-.', ':', 'None', ' ', ''])

As you will see in this tutorial, you can also generate line styles using colors and markers. What is more? Find out below.

Lab Setup To explore Line Styles In Matplotlib

Assume we want to plot the annual earnings of company X’s employees (designers, developers, and accountants) aged between 20 and 29. We store the ages in a list as follows.

ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

Next, we create lists for each group of employees’ salaries.

designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

developers = [55893, 53375, 52000, 51008, 58000, 58555, 59979, 60050, 65991, 67000]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000]

Now that we have some data to practice various line styles in matplotlib, let’s go ahead and manipulate the data.

Practical Ways To Use Line Styles In Matplotlib

➥Get the required functions

Install the matplotlib library using pip.

pip install matplotlib

# OR

pip3 install matplotlib

After installing Matplotlib, create a file and import the library’s functions into it. I have created one called employees.py and imported lines and pyplot as follows.

from matplotlib import lines, pyplot as plt

We will get the line styles from lines and plot the lines with pyplot. It is a convention to shorten pyplot as plt. In simple words it is an alias.

➥Plot the data

Plotting a bunch of data on a curve requires specifying the values for the x-axis and y-axis.

plt.plot(<x-axis data list>, <y-axis data list>)

We can plot our employee values as follows.

ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29] designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

developers = [55893, 53375, 52000, 51008, 58000, 58555, 59979, 60050, 65991, 67000]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000] plt.plot(ages, designers)

plt.plot(ages, developers)

plt.plot(ages, accountants) plt.show()

The plt.show() function instructs Python to reveal the graphical information cached in the memory. As soon as you run the file on the terminal, you get three solid lines of different colors.

python employees.py

Now let us label the lines and add a title to the plots for easier identification. Insert the code before the plt.show() line.

plt.xlabel("Ages")

plt.ylabel("Annual salary in USD")

plt.title("Salaries of X employees for 20-29 ages")

Output:

However, we cannot tell what the green, blue, and coral lines represent. So, let’s mark the lines using labels and a legend.

➤labels

plt.plot(ages, designers, label='designers')

plt.plot(ages, developers, label='developers')

plt.plot(ages, accountants, label='accountants')

➤legend represents the area that describes specific elements of the graph. In this case, we will use the legend() method to describe the labels assigned previously.

plt.legend()

plt.show()

Output:

Full code: Here’s the full code that helps to represent our data in the form of different lines.

from matplotlib import lines, pyplot as plt ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29] designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

developers = [55893, 53375, 52000, 51008, 58000, 58555, 59979, 60050, 65991, 67000]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000] plt.plot(ages, designers, label='designers')

plt.plot(ages, developers, label='developers')

plt.plot(ages, accountants, label='accountants') plt.xlabel("Ages")

plt.ylabel("Annual salary in USD")

plt.title("Salaries of X employees for 20-29 ages") plt.legend() plt.show()

Looks better, right? Yes, but we can improve the visuals by changing the line styles.

Change The Line Styles

We assigned different labels to distinguish different data but is there a way to change the style of the line? Yes! The first step is to grab the lines with the help of the lines module. You can import lines from matplotlib as we have done above or get them from Matplotlib line style docs.

Let’s print the styles from the imported lines. After commenting out the plt.show() method, run the print line below the import statement.

print(lines.lineStyles)

We get a dictionary which represents the type of styles in which the lines can be represented as follows:

{'-': '_draw_solid', '--': '_draw_dashed', '-.': '_draw_dash_dot', ':': '_draw_dotted', 'None': '_draw_nothing', ' ': '_draw_nothing', '': '_draw_nothing'}

Let’s find the keys and store them as list_styles.

line_styles = lines.lineStyles.keys()

We get a list on running printing line_styles.

print(line_styles)

dict_keys(['-', '--', '-.', ':', 'None', ' ', ''])

Let’s use the result to change line styles for the plots.

Combining the lines.lineStyles.keys() and pyplot.linestyle helps us change the designers and developers plots as follows.

from matplotlib import pyplot as plt ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29] designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

developers = [55893, 53375, 52000, 51008, 58000, 58555, 59979, 60050, 65991, 67000]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000] plt.plot(ages, designers, label='designers', linestyle='--')

plt.plot(ages, developers, label='developers', linestyle=':')

plt.show()

Output:

Here, lines.lineStyles show the styles, while pyplot‘s linestyle attribute changes the lines graphically.

Tidbits

• You can also style the lines using markers, width, and colors. For example, you can mark the accountants‘ plot using o as follows.

from matplotlib import pyplot as plt ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000]

plt.plot(ages, accountants, label='accountants', marker='o')

plt.show()

Output:

• You can increase the width of the designers plot from 1 to 3 as follows

from matplotlib import pyplot as plt ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

plt.plot(ages, designers, label='designers', linestyle='-.', linewidth=3)

plt.show()

Output:

• Lastly you can customize the plot colors using the color aliases, hex colors or names.

from matplotlib import pyplot as plt ages = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29]

designers = [45893, 50375, 52000, 52009, 54000, 55555, 56979, 57040, 55991, 54000]

developers = [55893, 53375, 52000, 51008, 58000, 58555, 59979, 60050, 65991, 67000]

accountants = [40000, 41500, 42000, 42508, 43001, 44555, 46979, 48050, 49991, 51000]

plt.plot(ages, designers, label='designers', linestyle='-.', color='b')

plt.plot(ages, developers, label='developers', linestyle=':', linewidth=3, color='#6dee6d')

plt.plot(ages, accountants, label='accountants', marker='o', color='gold')

plt.show()

Output:

Conclusion

You can get a list of styles in matplotlib using the lines attribute. After storing the target styles, you can change the lines’ appearance using pyplot‘s built-in linestyle attribute. Additionally, as illustrated in this tutorial, you can differentiate lines using markers, width, and colors.

Recommended: Matplotlib — A Simple Guide with Videos

Please stay tuned and subscribe for more interesting discussions in the future. Happy learning!

PHP session is one of the methods for keeping data persistency on the server side.

PHP sessions have a deadline time limit for keeping data persistent. PHP configuration file includes directives to have this specification.

We can also create custom code to change the default PHP session deadline.

This article contains sections that describe the PHP sessions, their time-limit configurations. It provides examples for setting session limits and tracking existence.

The below example gives a quick solution to set PHP session time. It contains only two steps to set and track the session expiration status.

<?php

session_start();

//Set PHP session with value, time

$currentTime = time();

$_SESSION['color'] = array( "value" => "blue", "time" => $currentTime, "life_time" => 5

);

?>

<?php

session_start();

if (isset($_SESSION['color'])) { $sessionSetTime = $_SESSION['color']['time']; $sessionLifeTime = $_SESSION['color']['life_time']; if ((time() - $sessionSetTime) > $sessionLifeTime) { unset($_SESSION['color']); print 'Session expired'; }

}

?>

About PHP session

We have already seen PHP sessions and cookies in a previous article. PHP sessions are for managing application data, state persistent during the working flow.

There are a lot of uses of sessions in an application. The below list shows some of the states or data managed by the use of sessions.

We have seen how to create a login script using the PHP session. In that, the session lifetime tracking can be used to log out after few minutes of inactivity.

PHP session lifetime settings

This section describes the configuration directives used to set PHP session time. The below table shows two PHP.ini settings related to the session.

The below PHP info highlights the session configuration settings. Refer to more runtime session configuration directives in the linked official site.

Example: Working with PHP session time – Set expiration and limit lifetime

This PHP session time handling example is the enhanced version of the above quick example.

It creates three session variables to set color, shape and size. It sets the lifetime for each PHP session variable while setting values.

The PHP code checks if the session exists. Once the time is reached, it unset that particular session variable and destroys it.

Landing page to set session

The landing page of this example shows a control to set the PHP session time. Once started, the session expiration status is checked at a periodic interval. This page includes the AJAX script to raise the call to PHP to check the session.

If the PHP session time is over, then this page will display a notice to the user. After all the sessions are expired, then the page will clear the notification and ask to reset the session.

index.php

<html>

<head>

<link href="./assets/css/style.css" rel="stylesheet" type="text/css" />

</head>

<body> <div class="session" data-status='<?php if(!empty($_GET["status"])) { echo $_GET["status"]; } ?>'> <div id="box"> <h1 align="center">Set PHP session time</h1> <div class="text"> <a href="set-session.php" class="btn">Reset Session</a> </div> <div id="status"></div> </div> <div id="message"></div> </div> <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script> <script src="./assets/js/session.js"></script>

</body>

</html> 

Check PHP session time via JavaScript AJAX

This script sets an interval to call the AJAX script to check the PHP session time. After getting the response, this AJAX success block shows the expired PHP sessions.

It checks the PHP session time every 5 seconds via AJAX. This script uses JavaScript setInterval() to invoke the checkSession() method.

session.js

if($('.session').data('status') != "") { var interval; interval=setInterval(checkSession, 5000); $("#status").text("Checking session expiration status...");

}

function checkSession(){ $.ajax({ url:"check-session.php", method:"POST", success:function(response){ if(response!=""){ if(response == -1){ $("#status").hide(); clearInterval(interval); window.location.href='index.php'; } else{ $("#message").append(response); } } } });

};

Set unset PHP session time

In this section, it shows two PHP files to set and unset the PHP session time.

The set-session.php is called on clicking the UI control on the landing page. It sets the color, shape and size in the PHP session.

Each session array is a multi-dimensional associative array. It has the details of PHP session set time, lifetime and value.

The session set-time and lifetime are used to calculate the session expiry.

set-session.php

<?php

if (! isset($_SESSION)) { session_start();

}

$currentTime = time();

$_SESSION['color'] = array( "value" => "blue", "time" => $currentTime, "lifetime" => 3

);

$_SESSION['shape'] = array( "value" => "circle", "time" => $currentTime, "lifetime" => 5

);

$_SESSION['size'] = array( "value" => "big", "time" => $currentTime, "lifetime" => 10

);

header("Location: index.php?status=starts");

exit();

?> 

This code returns the response text once the session is expired.

It validates the session expiry by comparing the remaining time and the PHP session lifetime.

Once all three sessions are expired, then this code returns -1. On receiving -1, the AJAX callback stops tracking by clearing the interval.

check-session.php

<?php

if (! isset($_SESSION)) { session_start();

} if (! isset($_SESSION['color']) && (! isset($_SESSION['shape'])) && (! isset($_SESSION['size']))) { print - 1;

}

if (isset($_SESSION['color'])) { $sessionTimeColor = $_SESSION['color']['time']; $sessionLifeTimeColor = $_SESSION['color']['lifetime']; if ((time() - $sessionTimeColor) > $sessionLifeTimeColor) { unset($_SESSION['color']); print '<div class="response-text"><span>Color Session Expired</span></div>'; } } if (isset($_SESSION['shape'])) { $sessionTimeShape = $_SESSION['shape']['time']; $sessionLifeTimeShape = $_SESSION['shape']['lifetime']; if ((time() - $sessionTimeShape) > $sessionLifeTimeShape) { unset($_SESSION['shape']); print '<div class="response-text"><span>Shape Session Expired</span></div>'; } } if (isset($_SESSION['size'])) { $sessionTimeSize = $_SESSION['size']['time']; $sessionLifeTimeSize = $_SESSION['size']['lifetime']; if ((time() - $sessionTimeSize) > $sessionLifeTimeSize) { unset($_SESSION['size']); print '<div class="response-text"><span>Size Session Expired</span></div>'; }

}

exit();

?> 

Conclusion

Thus we have learned how to set PHP session time via programming. This article described the PHP configurations to set max session lifetime.

I hope this example helped to create your own code to manage PHP sessions and time.
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