jquery选择器使用优化

// Slower (the zero-based :even selector is a jQuery extension)
$( "#my-table tr:even" );

// Better, though not exactly equivalent
$( "#my-table tr:nth-child(odd)" );

$( ".data table.attendees td.gonzalez" );

// Better: Drop the middle if possible.
$( ".data td.gonzalez" );

// Fast:
$( "#container div.robotarm" );

// Super-fast:
$( "#container" ).find( "div.robotarm" );

$( ".buttons > *" ); // Extremely expensive.
$( ".buttons" ).children(); // Much better.

$( ":radio" ); // Implied universal selection.
$( "*:radio" ); // Same thing, explicit now.
$( "input:radio" ); // Much better.