Bug 622500

Is this still reproducible?

Yes.

The issue here is that in Java, float is 32-bit floating point, but in JavaScript, all numbers are 64-bit floating point.

Doubles don't show the same problem, because in Java they are 64-bit floating point.  The precision matches.

You probably know this, but to demonstrate the difference even just on Java side:

public class FloatDemo {
  public static void main(String[] args) {
    System.out.format("f1: %.20f%n", 7.81f);
    System.out.format("f2: %.20f%n", 7.81);
    if (7.81f == 7.81) {
      System.out.println("They are the same.");
    } else {
      System.out.println("They are not the same.");
    }
  }
}

So when adding the Float to script context in your example, it becomes the 64-bit representation of the (32-bit) 7.81f value, which is not the same as the 64-bit 7.81 value.

Strict equality comparisons between numbers that originate from different precision is rarely what you want to do.