Jash: JavaScript Shell

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A Cross-Browser Javascript Command-Line Debugging Tool

Features

Features List

• Command-line JavaScript execution
• DOM mouseover tool
• CSS Input Mode
• Tab-completion
• Command history
• Profiler (execution timer)
• Stop watch
• Object inspection
• Simple console output
• Skin-able
• Uses hotkeys.

Features Detail

• Command-line execution of javascript, in the scope of the current web page
• DOM mouseover tool
  • Shows node name, id, and class name of node under mouse pointer
  • Shows all parent nodes of node under mouse pointer
  • Stores node under mouse pointer in scope and automatically enters it into the input field, for easy manipulation
  • With InnerHTML Dump enabled, the DOM mouseover tool will also show a neatly-indented version of the current element's innerHTML property
• CSS Input Mode
  • Enables input of arbitrary css. Example:

    	#myDiv .myLi { background: purple; height: 32px; }
    	.dumbLink:hover { font: monospace; }
    			

  • In Firefox, rules can be applied / unapplied by turning css input mode on/off.
• Tab-completion
  • Pressing tab auto-completes your input based on the current window's scope
  • If more than one match is found, shows multiple matches
  • Completes javascript objects, element ids (when typing in document.getElementById), or element class names (when using certain functions) based on current window scope.
  • Completes element ids and element class names based on current window in CSS Entry mode
• Command history
  • Every command entered into the javascript input console is stored for easy retrieval.
  • Use the up / down arrow keys to navigate through command history
• Profiler (execution timer)
  • Runs performance checks on a given function. Reports the average milliseconds needed to execute a given function over a given number of executions. For example:

    	Input: 
    	f = function() { 
    		i=50000;
    		while(i>0) i--;
    	}
    	t = new Profiler(f);
    	t.multiPass(10);
    	
    	Output:
    	-------PROFILER----------------------------------------------
    	function () {
    		i = 50000;
    		while (i > 0) {
    			i--;
    		}
    	}
    	-------PROFILER----------------------------------------------
    	Type of profile: runOnce
    	Average execution time: 146ms
    	Average calculated from 10 pass(es)
    	-------PROFILER----------------------------------------------
    					

  • The Profiler.multiPass() method allows you to run looped code in a regular for loop or a reverse while loop, as well:

    	t.multiPass(10,"forLoop",100); 	//execute f() in a for loop of 100 iterations 10 times
    	t.multiPass(5,"reverseWhile",200); //execute f() in a reverse while loop of 200 iterations 5 times
    					

  • The Profiler will automatically store and average results for different types of executions. For example, if you do a multi-pass operation for 300 times, the Profiler will give you the average of all three hundred executions. If you do a multi-pass operation with a loop, Profiler will store results for that loop / iteration combination discretely from other loop/iteration combinations. For example,

    	t.multiPass(10,"forLoop",100);
    					

    will necessarily have different results from

    	t.multiPass(10,"forLoop",200);
    					

    as the latter loops 100 more times than the former. Profiler recognizes this and stores their results discretely.
• Stop watch
  • The stopWatch object can be used to time execution speeds - useful during script optimization

    	jash.stopWatch.start();
    	while(i>0) {
    		//something 
    		i--;
    	}
    	jash.print(jash.stopWatch.stop());
    					

• Object inspection
  • The dump() method prints the names and contents of all members of an object
  • The show() method prints the names and types of all members of an object

  	jash.dump(window);		//be prepared to see a ton of stuff 
  	jash.show(window);		//easier to scan large objects with
  				

• Simple console output
  • The console has a print() method, which prints a line of arbitrary text and optionally clears the console before doing so. This is probably the most used method when using the console to debug scripts during execution (think of it as a practical and more useful replacement to "alert()").

    	var thing = (Math.random() * 1000) % 456;
    	if(thing > 400) {
    		jash.print("thing is more than 400...");
    		//something useful happens...
    	}
    					

• Skin-able
  • Jash is built in the current document with XHTML and CSS. Jash uses a simple table-less layout and incorporates an external stylesheet to control how it looks. You can easily change the appearance of the debugger using CSS by changing the stylesheet or using your own stylesheet.
• Uses hotkeys. In Firefox 2.0, use Alt-Shift instead of Alt. Macintosh users, replace the alt key with the control key.
  • Alt-X to turn on/off DOM mouseover tool
  • Alt-S to turn on/off CSS input mode
  • Alt-C clears the input and output
  • Alt-Z executes the current input
  • Alt-Q enables/disables transparent mode
  • Esc hides/shows Jash
  • Arrow up and arrow down retrieve the last or next command entered into the console, respectively.