passing php string with multiple lines to a javascript function/variable

Pass the string into json_encode to properly escape it. If you're outputting to an HTML document, make sure to pass JSON_HEX_TAG as part of the options, to escape < and > and prevent a malicious user from ending your </script> tags early and introducing an XSS exploit.

try this

var JsString = "<?php 
echo str_replace(array("\n","\r","\r\n"),'','YOUR 
MULTI LINE 
STRING');?>";