Analyze Jank

gistfile1.txt

#!/usr/bin/env node
var path = require('path')
, fs = require('fs');
file = ''
stream = fs.createReadStream( path.normalize( process.argv[ 2 ] ) );
stream.on( 'data', function(data) {
    file += data.toString();
} );
stream.on( 'end', function() {
    stream = JSON.parse( file );
    var x = 0, xlen = stream.length, jank_ct = 0, jank_paths = {};
    for(; x < xlen; x += 1) {
        item = stream[ x ];
        /*console.log( item );*/
        var children = item.children, y = 0, ylen = ( 'undefined' !== typeof children ) ? children.length : 0, previous = null, child = null;
        for(; y < ylen; y += 1) {
            child = children[ y ];
            var since = 0;
            if ( null !== previous ) {
                since = child.startTime - previous.endTime;
                if( !isNaN( since ) ) {
                    if( since > 16.6 ) {
                        jank_ct++;
                        z = 0, zitems = item.children || [], zlen = zitems.length, chain = [];
                        for(; z < zlen; z += 1 ) {
                            ch = zitems[ z ];
                            chain.push(ch.type)
                        }
                        key = chain.join(' -> ')
                        if ('undefined' === typeof jank_paths[ key ] ) {
                            jank_paths[ key ] = 1;
                        } else {
                            jank_paths[ key ]++;
                        }
                    }
                }
            }
            /*console.log( child );*/
            previous = child;
        }
    }
    console.log( jank_paths  );
} );