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?

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