It was also a rarely-used classic way to deal with variable references that changed in a loop:

  var values = [];
  for (var i = 0; i < 3; i++) {
    values.push(function() { console.log(i); });
  }
  for (var j = 0; j < 3; j++) {
    values[j]();
  }

This would log 3, 3 times. The usual fix (before the variety of modern ways) was to use an IIFE in the first loop:

  for (var i = 0; i < 3; i++) {
    (function(i) {
      values.push(function() { console.log(i); });
    })(i);
  }

Alternatively, this works:

  for (var i = 0; i < 3; i++) {
    with ({i: i}) {
      values.push(function() { console.log(i); });
    }
  }