var jcnt = function (str, num, lst) { len = 0; for (i=0; i<str.length; i++) { if (escape(str.charAt(i)).substring(0, 2) == "%u") { len++; } len++; if (len >= num) { str = str.substring(0,i+1)+lst; break; } } return str; } var str = "あいうえおabcdeかきくけこ12345"; alert(jcnt(str,13,"..."));