if (indexisbn.indexOf("978") == 0) {isbn = isbn.substr(3,9);var xsum = 0;var add = 0;var i = 0;for (i = 0; i < 9; i++) {add = isbn.substr(i,1);xsum += (10 - i) * add;}xsum %= 11;xsum = 11 - xsum;if (xsum == 10) { xsum = "X"; }if (xsum == 11) { xsum = "0"; }isbn += xsum;}希望本文所述对大家的javascript程序设计有所帮助。