Positive Number to Negative Number in JavaScript

Question

Basically  the reverse of abs  If I have   if   this find   pdxslide-activeSlide   index    lt  slideNum - 1      slideNum   -slideNum   console log slideNum    No matter what console always returns a positive number  How do I fix this   If I do   if   this find   pdxslide-activeSlide   index    lt  slideNum - 1       selector animate       left   -slideNum   sizes images width     px       750   InOutPDX     else      selector animate       left   slideNum   sizes images width     px       750   InOutPDX       it works tho  but it s not  DRY  and just stupid to have an entire block of code JUST for a -

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The basic formula to reverse positive to negative or negative to positive   i -  i   2

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var x   100  var negX     -x         gt  -100

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In vanilla javascript    x000D   x000D  if number  gt  0  x000D    return -1 number  x000D   x000D   x000D    Where number above is the positive number you intend to convert   This code will convert just positive numbers to negative numbers simple by multiplying by -1

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The reverse of abs is Math abs num    -1

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To get a negative version of a number in JavaScript you can always use the   bitwise operator   For example  if you have a   1000 and you need to convert it to a negative  you could do the following   a    a   1    Which would result in a being -1000

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var i   10  i   i   -1    Result  -10  var i   -10  i   i   -1    Result  10  If you divide by negative 1  it will always flip your number either way

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Math abs num    gt  Always positive -Math abs num    gt  Always negative   You do realize however  that for your code  if  this find   pdxslide-activeSlide   index    lt  slideNum-1   slideNum   -slideNum   console log slideNum    If the index found is 3 and slideNum is 3  then 3  lt  3-1    false so slideNum remains positive    It looks more like a logic error to me

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num   -1   This would do it for you

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Are you sure that control is going into the body of the if  As in does the condition in the if ever hold true  Because if it doesn t  the body of the if will never get executed and slideNum will remain positive  I m going to hazard a guess that this is probably what you re seeing   If I try the following in Firebug  it seems to work    gt  gt  gt  i   5  console log i   i   -i  console log i   5 -5   slideNum    -1 should also work  As should Math abs slideNum    -1

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It will convert negative array to positive or vice versa  function negateOrPositive arr        arr map res   gt  -res

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Javascript has a dedicated operator for this  unary negation    TL DR  It s the minus sign    To negate a number  simply prefix it with - in the most intuitive possible way  No need to write a function  use Math abs   multiply by -1 or use the bitwise operator   Unary negation works on number literals   let a   10      a is  10  let b   -10     b is  -10    It works with variables too   let x   50  x   -x          x is now  -50   let y   -6  y   -y          y is now  6    You can even use it multiple times if you use the grouping operator  a k a  parentheses   l   10           l is  10  m   -10          m is  -10  n   - 10         n is  -10  o   - - 10       o is  10  p   - -10        p is  10   double negative makes a positive    All of the above works with a variable as well

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If you don t feel like using Math Abs   -1 you can you this simple if statement  P  if  x  gt  0        x   -x      Of course you could make this a function like this  function makeNegative number        if  number  gt  0            number   -number            makeNegative -3     -3 makeNegative 5     -5  Hope this helps  Math abs will likely work for you but if it doesn t this little

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Use 0 - x  x being the number you want to invert

[javascript] Positive Number to Negative Number in JavaScript?

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