Dang is versatile - it can be used to express anger or frustration at something for example "Oh dang!" or in extreme cases an anger dang is a volatile shouting of the word, thereby eliminating the need for swearing.
On the flip side it can be used to expressed interest, suprise or acceptance to something, again phrased as "oh dang" but softer, with less inflection.
The word dang is also in common use in America, as an alternative to darn or damn.
A variation of the ever-popular damn.
Used mostly by old people, as (according to them) damn is too harsh a swear word to be uttered.
Used to show great frustration or annoyance or to reinforce/exclaim a point.