sandip chitale's blog

NOTE: I have moved many of my modules to NetBeans Plugin Portal . Please check there for latest versions of modules described on this blog.

« Firefox add-on -... | Main | Remove unused bindin... »

Wednesday January 23, 2008

Improved Callstack information in JavaScript

In this post I blogged about a simple function to get the call stack in JavaScript. Here is an improved variant of the same function:

/**
 * This function returns an array of objects that contain the information about call stack.
 */
function callstack() {
    function StackFrame(funcName, funcSource, flName, lnNumber) {
        this.functionName = funcName;
        this.functionSource = funcSource;
        this.fileName = flName;
        this.lineNumber = lnNumber;
    }
    StackFrame.prototype.toString = function() {
        return 'at ' + this.functionName + '(' + this.fileName + ':' +  this.lineNumber + ')' ;
    };
    StackFrame.prototype.toHtml = function() {
        return '<table border="0">' +
        '<tr valign="top"><td><b>Name:  </b></td><td>'           + this.functionName                + '</td></tr>' +
        '<tr valign="top"><td><b>File:  </b></td><td>'           + this.fileName                    + '</td></tr>' +
        '<tr valign="top"><td><b>Line:  </b></td><td>'           + this.lineNumber                  + '</td></tr>' +
        '<tr valign="top"><td><b>Source:</b></td><td>' +
        ( this.functionSource ?
          '<pre>' + this.functionSource.toString().replace(/\</g, '&lt;').replace(/\>/g, '&gt;') + '</pre>' :
          'unavailable')                                                                            + '</td></tr>' +
        '</table>'
        ;

    };
    var stackFrameStrings = new Error().stack.split('\n');
    // remove first two stack frames
    stackFrameStrings.splice(0,2);
    var stackFrames = [];
    for (var i in stackFrameStrings) {
        // a stack frame string split into parts
        var stackFrame = stackFrameStrings[i].split('@');
        if (stackFrame && stackFrame.length == 2) {
            stackFrames.push(
            // Stackframe object
            new StackFrame(stackFrame[0],
                           eval(stackFrame[0].replace(callstack.sansParenthesisRE,'')),
                           stackFrame[1].match(callstack.fileNameLineNumberRE)[1], // first group
                           stackFrame[1].match(callstack.fileNameLineNumberRE)[2]  // second group
            )
            );
        }
    }
    return stackFrames;
}
callstack.sansParenthesisRE = /[(][^)]*[)]/;
callstack.fileNameLineNumberRE = /(.*):(\d+)$/;

Here is how it canbe used. The callstack function code above is assumed to be stored in a file named Utilities.js .

<html>
<head>
<title>Callstack</title>
<script src='Utilities.js'></script>
<script>
function called() {
    var cs = callstack();
    document.write(cs[0].toHtml());
    document.write(cs[1].toHtml());
    document.write(cs[2].toHtml());
}
function caller() {
	called(); 
}
</script>
</head>
<body onload="caller();">
</body>
</html>

Here is the output as displayed in the browser (FireFox):

Name:	called()
File:	file:///languages/javascript/Callstack.html
Line:	7
Source:	function called() { var cs = callstack(); document.write(cs[0].toHtml()); document.write(cs[1].toHtml()); document.write(cs[2].toHtml()); }

Name:	caller()
File:	file:///languages/javascript/Callstack.html
Line:	13
Source:	function caller() { called(); }

Name:	onload([object Event])
File:	file:///languages/javascript/Callstack.html
Line:	1
Source:	function onload(event) { caller(); }

Posted by sandipchitale ( Jan 23 2008, 07:46:59 AM PST ) Permalink Comments [0]

Trackback URL: http://blogs.sun.com/scblog/entry/improved_callstack_information_in_javascript

Comments: