var str1 = "1111111111111111";
var str2 = "2222222222222222222";

var s = str1.concat(str2);

document.write("the first String is:"+str1+"< br>< br>\n");

document.write("the second String is:"+str2+"< br>< br>\n");

document.write("the concat result is:"+s+"< br>< br>\n");