JavaScript closures surprising

Question

var a = [];
var b = ['abc','def'];
for(var c of b) {
  var c_ = c.slice();
  a.push(function(){alert(c_)});
}

a[0]();
a[1]();

Result is seing the message "def" twice. This is entirely unexpected. How do I do this in JavaScript? If it were alert(c) I could understand but c_ is clearly a copy of c and is properly scoped by other language's standards.

Answer 1

var is always function scoped. let is block scoped!.