Doesn't work in IE

This little function opens links in a new window in all browsers except IE / Edge:

function externalLinks() {
for(var c = document.getElementsByTagName("a"), a = 0;a < c.length;a++)
{ var b = c[a]; b.getAttribute("href") && b.hostname !== location.hostname && (b.target = "_blank") } } ; externalLinks();

Code (markup):

Does anyone know why?

 

Got it working by changing b.hostname to b.href.hostname

 

Probably WAY too late, but did you REALLY mean to assign b.target to __blank, or is that supposed to be ==?