Javascript toLowerCase strange behaviour

I have a small application that reads tweets and tries to match keywords and I noticed this strange behaviour with a particular string:

var text = "The Νіk​е D​un​k​ Ніgh ЅΒ 'Uglу Ѕwеаt​еr​' іѕ n​оw аvаіlаblе http://swoo.sh/IHVaTL";
var lowercase = text.toLowerCase()

Now the value of lowercase is:

the νіk​е d​un​k​ ніgh ѕβ 'uglу ѕwеаt​еr​' іѕ n​оw аvаіlаblе http://swoo.sh/ihvatl

So it seems like the string is in a weird format, I double checked some of the letters and found that:

text.charAt(4)
>"N"
text.charCodeAt(5)
>925
'N'.charCodeAt(0)
>78

So even if it looks like a normal N, the unicode associated to it corresponds to

0925 थ DEVANAGARI LETTER THA

according to the unicode chart

So I´m a bit puzzled about how this can happen, and if there is anyway to "convert" to the supposed real letter