More better now ;-)

It can be dangerous in this case if, for example, you are executing this code on your server based on user input.

its only dangerous when missusing it :) often peapole dont even know that they us it, because its hidden in other functions ;)

This is not a JS problem. It is a floating point problem, it happens on other languages.

0.2 + 0.1 == 0.30000000000000004
It's a well known issue of JS itself

just a try, for 0.1+0.2=0.3
but it doesn't work

You should not be using eval, it is dangerous.

It's not perfect ;-)
Try that:

it("should sum only numbers and calculate the correct number", function(){
    Test.assertEquals(sum([5, '3', 2, '$', 1, NaN]), 8, "Sum equals to 8");
    Test.assertEquals(sum(['3', 0.2, '$', 0.1]), 0.3, "Sum equals to 0.3");
});