I like using the command line / shell to pass information to scripts and programs. Sure it has limitations but it’s generally pretty effective.

Each language seems to have it’s own method of handing them, and CasperJS does not seem to be any different. What I did find a little different from others, is how CapserJS splits out arguments from parameters (options in CapserJS speak).

Passing Arguments

Passing arguments is a fairly simple affair. His an example of passing some arguments on the command line to a screen capture utility I’m working on:

casperjs generic.screenshot.cjs http://www.someplace.com save_local
[
“http://www.someplace.com”,
“save_local”
]

They are placed into a list (integer indexed array), and can be addressed in the following way:

url = casper.cli.args[0];
mode = casper.cli.args[1];

This would result in ‘url’ = ‘http://www.someplace.com’ and ‘mode’ = ‘save_local’. Pretty straight forward. One major drawback, you must know the order of the parameters, add a new one, get one out of place and the entire house of cards collapses.

There is a better way!

Passing Parameters (options)

Passing options is a fairly simple affair as well. His an example of passing some option on the command line:

casperjs generic.screenshot.cjs –url=http://www.someplace.com –mode=save_local
{
“casper-path”: “/opt/casperjs”,
“cli”: true,
“url”: “http://www.someplace.com”,
“mode”: “save_local”
}

Note: “casper-path” and “cli” are injected automatically

They are placed into an array, and can be addressed in the following way:

url = casper.cli.options[‘url’];
mode = casper.cli.options[‘mode’];

This would result in ‘url’ = ‘http://www.someplace.com’ and ‘mode’ = ‘save_local’. Now, you do not need to worry about ordering of options, and adding more options doesn’t mean that you’ll have to worry about re-coding the variable localization, ordering etc. It’s also CLEAR to any user how the cli is formatted.

Now, go forth and parse, screen capture and automate your testing until your heart is content!