YellowLabTools/lib/tools/phantomas/custom_modules/modules/javaScriptBottleYLT/javaScriptBottleYLT.js

/**
 * Reports the use of functions known to be serious performance bottlenecks in JS
 *
 * @see http://www.nczonline.net/blog/2013/06/25/eval-isnt-evil-just-misunderstood/
 * @see http://www.quirksmode.org/blog/archives/2005/06/three_javascrip_1.html
 * @see http://www.stevesouders.com/blog/2012/04/10/dont-docwrite-scripts/
 *
 * Run phantomas with --spy-eval to count eval() calls (see issue #467)
 */
/* global document: true, window: true */

exports.version = '0.2';

exports.module = function(phantomas) {
    'use strict';
    
    phantomas.setMetric('documentWriteCalls'); //@desc number of calls to either document.write or document.writeln @offenders
    phantomas.setMetric('evalCalls'); // @desc number of calls to eval (either direct or via setTimeout / setInterval) @offenders

    // spy calls to eval only when requested (issue #467)
    var spyEval = phantomas.getParam('spy-eval') === true;
    if (!spyEval) {
        phantomas.log('javaScriptBottlenecks: to spy calls to eval() run phantomas with --spy-eval option');
    }

    phantomas.on('init', function() {
        phantomas.evaluate(function(spyEval) {
            (function(phantomas) {
                function report(msg, caller, backtrace, metric) {
                    phantomas.log(msg + ': from ' + caller + '!');
                    phantomas.log('Backtrace: ' + backtrace);

                    phantomas.incrMetric(metric);
                    phantomas.addOffender(metric, "%s from %s", msg, caller);
                }

                // spy calls to eval()
                if (spyEval) {
                    phantomas.spy(window, 'eval', function(code) {
                        report('eval() called directly', phantomas.getCaller(), phantomas.getBacktrace(), 'evalCalls');
                        phantomas.log('eval\'ed code: ' + (code || '').substring(0, 150) + '(...)');
                    });
                }

                // spy calls to setTimeout / setInterval with string passed instead of a function
                phantomas.spy(window, 'setTimeout', function(fn, interval) {
                    if (typeof fn !== 'string') return;

                    report('eval() called via setTimeout("' + fn + '")', phantomas.getCaller(), phantomas.getBacktrace(), 'evalCalls');
                });

                phantomas.spy(window, 'setInterval', function(fn, interval) {
                    if (typeof fn !== 'string') return;

                    report('eval() called via setInterval("' + fn + '")', phantomas.getCaller(), phantomas.getBacktrace(), 'evalCalls');
                });

                // spy document.write(ln)
                phantomas.spy(document, 'write', function(arg) {
                    report('document.write() used', phantomas.getCaller(), phantomas.getBacktrace(), 'documentWriteCalls');
                });

                phantomas.spy(document, 'writeln', function(arg) {
                    report('document.writeln() used', phantomas.getCaller(), phantomas.getBacktrace(), 'documentWriteCalls');
                });
            })(window.__phantomas);
        }, spyEval);
    });
};