JavaScript is a high-level scripting language that has become one of the core components of the World Wide Web.
Originally used client side in a user’s browser, it has migrated back to the server and is also used for general scripting purposes.
Windows
JavaScript is one of many languages supported by the Windows Scripting Host (WSH).
Hello World
The following is a JavaScript program using the Windows Scripting Host.
The file is called helloworld.js.
WSH.Echo("Hello world");
WSH.Quit();
Create the file with your favourite plain text editor (Notepad or better, but not a word processor, they tend to add lots of tat).
Save the file.
Bring up the command line interface (search for cmd).
Use the change directory command to move to where you have saved the file (if you have spaces in the folder names, enclose the path in double quotes).
To execute the file type:
cscript helloworld.js
This is what you will get (Windows 10 machine - YMMV)
C:\some\folder\tree>cscript helloworld.js
Microsoft (R) Windows Script Host Version 5.812
Copyright (C) Microsoft Corporation. All rights reserved.
Hello world
C:\some\folder\tree >
An alternative is to use a WSF file (.wsf). This requires the <job> or <package> tags around the script. Because WSF files could contain any supported language (or indeed multiple languages) you need to define the language within a script tag.
<job>
<script language="JScript">
WSH.Echo("Hello world");
WSH.Quit();
</script>
</job>
C:\some\folder\tree >cscript helloworld.wsf
Microsoft (R) Windows Script Host Version 5.812
Copyright (C) Microsoft Corporation. All rights reserved.
Hello world
C:\some\folder\tree >
HTML
The following is extremely simple.
The script is executed when the page is loaded but before it is displayed. It is possible to execute the JavaScript after the page has loaded or in response to some event.
<!DOCTYPE html>
<html>
<head>
<title>Javascript in HTML</title>
</head>
<body>
<p>Testing Javascript</p>
<script language="JScript">
alert("Hello world!");
</script>
</body>
</html>
Save the file as helloworld.html.
Because this is displayed in your browser, the display will vary.
Linux
Raspberry Pi
From Raspbian Stretch onwards, most standard installs of Raspbian come with node.js installed as standard.
You can check if it is installed by running:
node -v
On the command line. If it is installed, it will return the version number.
If your installation does not have node.js, install using:
sudo apt-get install node
sudo apt-get install npm
The program is just one line:
console.log("Hello world!");
Using terminal, change the directory to where you have saved the file, you can run it by typing:
node helloworld.js
The result will be similar to:
pi@raspberrypi:~/Documents/JavaScript $ node helloworld.js
Hello world!
pi@ raspberrypi:~/Documents/JavaScript $
Useful functions
Splitting Strings
The following is a Windows specific example.
WSH.Echo("Test code");
WSH.Echo(splitString("-2MKptcmt1Q,W3XlnfNPk6I,dRYRcM-HHvY"));
function splitString(aString){
WSH.Echo(aString);
result = "";
anArray=[];
anArray = aString.split(",");
for(ix = 0;ix<anArray.length;ix++){
result = result +"*" +(anArray[ix])+"*";
}
return result;
}
References
https://en.wikipedia.org/wiki/JavaScript
https://en.wikipedia.org/wiki/ECMAScript
https://www.w3schools.com/js/default.asp
https://www.w3schools.com/jsref/default.asp
https://en.wikipedia.org/wiki/Windows_Script_Host
https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/cscript
https://docs.microsoft.com/en-us/previous-versions//98591fh7(v=vs.85)
https://www.instructables.com/id/Javascripting-Your-RaspberryPi/
