Subtract my odds from my evens
Jelly, 6 bytes

-*æ.¹A


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How it works

-*æ.¹A  Main link. Argument: A (digit array)

-*      Raise -1 to A's digits, yielding 1 for even digits and -1 for odd ones.
    ¹   Identity; yield A.
  æ.    Take the dot product of the units and the digits.
     A  Apply absolute value.