The JavaScript programming language

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Here is some background on JavaScript.

JavaScript is a scripting language that is typically embedded in HTML web pages to provide client-side processing at the web browser. JavaScript is:

a textual language that is interpreted, not compiled.
similar in spirit to Visual Basic but with functional capabilities
embedded as text in an HTML page.
used to extend the functionality of HTML pages on the client side.

JavaScript is also a server-side or command line language, as used in node.js.

There are many names for JavaScript.

ECMAScript is the formal name form the ECMA (European Computer Manufacturers Association) .
LiveWire was Netscape's original name for JavaScript.
Microsoft's version of JavaScript was JScript

Java and JavaScript have a superficially similar syntax that is loosely based on C++.

Java is a very nice object-oriented programming language that started as a failed toaster language (i.e., intended for embedded systems).
Sun Microsystems used Java to take advantage of the popularity of the web.
Netscape asked Sun if they could call their scripting language JavaScript.

Java was supposed to rule the Internet.

Java was a failed toaster (embedded systems) language.
Java was a failed Internet language (JavaScript won the battle).
Java is used in enterprise (entire organization) computing (as a platform independent language).
Java is used in Android development (though Google would like this changed).

JavaScript was developed in a few weeks and rushed to market - good and bad parts.

JavaScript had a lot of ML functional language concepts in it - which helped it adapt and win the Internet battle with Java.

JavaScript is often used as a scripting language in other applications, much like Lua and VBScript.

The JSON (JavaScript Object Notation) is a common data exchange format, based on the data format of JavaScript.

Oracle, which bought out Sun Microsystems, has the trademark for the JavaScript name.

Node.js is a server-side JavaScript system that can also be used for command line application scripting purposes.

What follows are some node.js JavaScript program examples.

The file type of a JavaScript program file is js.

The following Linux command(s) create/edit a hello program in the your home directory using the nano text editor.

nano ~/hello.js

Create the following program text in the editor that will output the text "Hello world"

console.log("Hello world");

To exit with save, remember to press Ctrl-X, then "y" (for yes) and Enter to exit.

The following Linux command(s) run the program.

node ~/hello.js

The output should be as follows.

Hello world

Let us look at a program to implement to algorithm for decimal to binary conversion.

The routine toBinary1 takes as input a value and returns the string representation in binary (base 2)

The first part of the program will use the hard-coded value of 156.

The second part will use a loop to output the decimal values and binary representations of the values from 0 to 16.

Here is the JavaScript code.

function toBinary1(x1) {
	var s2 = "";
	if (x1 == 0) {
		s2 = "0";
		}
	else {
		while (x1 != 0) {
			var r1 = x1 % 2;
			x1 = Math.floor(x1 / 2);
			s2 = r1 + s2;
			}
		}
	return s2;
	}
var x1 = 156;
var s1 = toBinary1(x1);
console.log("Value "+x1+"d in binary is "+s1+"b.\n");
console.log("\n");
for (i1=0; i1 <= 16; i1++) {
	s1 = toBinary1(i1);
	console.log(i1+"d == "+s1+"b\n");
	}

Here is the output of the JavaScript code.

Value 156d in binary is 10011100b.



0d == 0b

1d == 1b

2d == 10b

3d == 11b

4d == 100b

5d == 101b

6d == 110b

7d == 111b

8d == 1000b

9d == 1001b

10d == 1010b

11d == 1011b

12d == 1100b

13d == 1101b

14d == 1110b

15d == 1111b

16d == 10000b