JSDev

JSDev, A JavaScript Development Tool

Douglas Crockford
douglas@crockford.com

2012-01-05

JSDev is a filter that activates selected comments, making them executable.
This makes it possible to put development, performance, and testing scaffolding
into a source file. The scaffolding is removed by minification, but is activated
by JSDev.

JSDev is a filter that takes a source file and looks for tagged comments in
either of these forms:

/ /

/() /

There can be no space between the /* and the . There can be no space
between the and the (. The content of tagged comment may not include
comments, nor can it contain strings or regular expression literals that
contain */. So, write

/debug(/[a-z][a-z0-9]/.test(variable))
console.log("*/ test");
*/

as

/debug(/[a-z][a-z0-9](?:)/.test(variable))
console.log("*\/ test");
*/

JSDev is given a list the names of the tags that should be activated.
Also, methods can be defined by following the tag name with : and a method
name. There can be no spaces around the :.

Replacement / /

tag form { }
method form {( );}

If a condition was included, then the replacement will be preceded with an
if statement.

The implementation in C obtains the input from stdin, and provides the result
to stdout. The tag list is taken from the command line. The command line can
also include a -comment specification. JSDev will exit(1) if there is an error.

In JavaScript, it is available as the JSDEV function that takes a source,
an array of tags, and an optional array of comments. It will throw an
exception if there is an error.

C command line example:

jsdev -comment "Devel Edition." output test_expose enter:trace.enter exit:trace.exit unless:alert

JavaScript:

output = JSDEV(input, [
"test_expose",
"enter:trace.enter",
"exit:trace.exit",
"unless:alert"
] , ["Devel Edition."]);

input:

// This is a sample file.

function Constructor(number) {
/enter 'Constructor'/
/unless(typeof number !== 'number') 'number', "Type error"/
function private_method() {
/enter 'private_method'/
/exit 'private_method'/
}
/*test_expose
this.private_method = private_method;
*/
this.priv = function () {
/enter 'priv'/
private_method();
/exit 'priv'/
}
/exit "Constructor"/
}

output:

// Devel Edition.
// This is a sample file.

function Constructor(number) {
{trace.enter('Constructor');}
if (typeof number !== 'number') {alert('number', "Type error");}
function private_method() {
{trace.enter('private_method');}
{trace.exit('private_method');}
}
{
this.private_method = private_method;
}
this.priv = function () {
{trace.enter('priv');}
private_method();
{trace.exit('priv');}
}
{trace.exit("Constructor");}
}

lightly minified:

function Constructor(number) {
function private_method() {
}
this.priv = function () {
private_method();
}
}