Question

how do I take the string using jQuery

Standard Class

and turn it into this

Standard_Class

if this is the id

$('#some_id').text;

Answer 1

Why do everything needs to be done with jQuery? How about a regex:

var result = 'Standard Class'.replace(/\s/g, '_');

and to modify the text into an existing element jQuery could be useful:

$('#some_id').text($('#some_id').text().replace(/\s/g, '_'));