How to add selective js on the page load? I have initialized four js files in .info file.Now on a single page if i want to load only two of .js files not all ,how can i do this?
JS included in your theme's .info file will be loaded on every page, there's no option to make them conditional (that I know of).

If you have files that need to be conditionally loaded you should do so in your theme's template.php file (perhaps in a hook_preprocess_page() function), and use drupal_add_js():

function MYTHEME_preprocess_page(&amp;$vars) {
  if ($some_condition) {
    $path = drupal_get_path('theme', 'MYTHEME') . '/path/to/file.js';
    drupal_add_js($path);
  }
}