Using get_option() in JavaScript

Define an array of parameters to be injected into the script:

$script_params = array(
    'myWidth' => get_option('my_width')
);

Localize the script via wp_localize_script:

wp_localize_script( 'your-script-handle', 'scriptParams', $script_params );

scriptParams now is a js object you can access from within the script:

alert( scriptParams.myWidth ); // the value from the PHP get_option call in the js