The ESP Standard Environment

Each HTTP request to an ESP web page causes a standard environment to be created that represents the state of the request, the server, form data, uploaded files and any client session state. ESP automatically creates this environment so that many web tasks can be accomplished without programming.

The ESP Standard Environment pre-defines a set of request global variables and functions. These are variables are private to the request, but global in scope so that all functions and classes can access their data within an ESP page without any C or C++ required coding.

See the Embedded Server Pages JavaScript API Reference for full ESP / EJS API documentation.

JavaScript Variables

The ESP run-time defines the following JavaScript variables for use inside an ESP page.

Variable Name	Description
application []	Stores user defined application data and is shared across all requests
cookies []	Request cookies supplied by the client with the request
false	False boolean value
files []	Uploaded files supplied by the client with the request
form []	Client form data. Includes both query string and posted data
global	Global variables for this request
headers []	HTTP request headers
Infinity	Floating point number set to Infinity
local	Local variables for the outermost JavaScript block in the ESP web page
Nan	Floating point number set to "Not a Number"
null	Defined variable set to Null
request []	Request details
server []	Server details
session []	Session state data for the current client. May be shared across multiple requests for a given client
true	True boolean value
undefined	Variable has no value and is set to the Undefined Value

JavaScript Functions

ESP defines the following global functions for use inside an ESP page.

Script Name	Syntax	Examples	Description
Array	Array(elt1, elt2, ...) Array(size)	var o = new Array("item 1", "item 2"); var o = new Array(256);	Create an array and insert elements. The second form creates an array with elements named "0", "1", "2", and so forth up to the nominated size.
assert	assert(condition)
createSession	createSession(timeout);	createSession(1800);	Create session state for this client. No effect if a session has aleady been created. This creates a session cookie that is sent to the client in the response. The timeout is in seconds.
destroySession	destroySession()	destroy(Session);	Terminate the current session.
eval	eval(script);	eval("var " + x + " = " + string);	Evaluate the given script.
exit	exit(status)	exit(0);	Immediately terminate the current script or ESP.
include	include(filename);	include("myLib.js");	Server side inclusion of a JavaScript library. The nominated file is read and parsed inline when the page is compiled by AppWeb.
Object	Object();	var o = new Object();	Create a new object.
print	print(string, ...);	print("Hello World\n");	Print the given strings to the web server standard output.
println	print(string, ...);	print("Hello World");	Print the given strings to the web server standard output followed by a new line.
printVars	print(v, ...);	print(obj1, obj2, obj3);	Print the string representation of the given objects to the web server standard output. Objects are expanded and all properties are printed. Great for debugging.
redirect	redirect(url, [code]);	redirect("notFound.html", 302); redirect("pageTwo.esp");	Redirect the client's browser to a new page.
refCount	refCount(o);	var count = refCount(obj);	Return the number of references to this object.
setHeader	setHeader("myHeader: true");		Set a HTTP header in the ESP response to the client.
trace	trace(message); trace(level, message);	trace(2, "Message at level 2");	Write a message to the AppWeb log.
useSession	useSession(timeout);	useSession(1800);	This is an alias for createSession.
write	write(args, ...);	write("Hello World"); write("<h1>Today is ", date);	Write the given arguments back to the client (browser) in the place of the ESP script. Multiple calls to write and its derivatives may be used.