What is the purpose of a plus symbol before a variable

Question

this really sounds like a simple question but I had no luck searching  what does the  d in   function addMonths d  n  keepTime         if   d      means

User · Answer

It is a unary     operator which yields a numeric expression  It would be the same as d 1  I believe

User · Answer

Operator   is a unary operator which converts value to number  Below I prepared a table with corresponding results of using this operator for different values   ----------------------------- -----------    Value                            Value     ----------------------------- -----------    1                             1              -1                           -1             3 14                         3 14           3                            3              0xAA                         170           true                          1             false                         0             null                          0              Infinity                     Infinity       infinity                     NaN            10a                          NaN           undefined                     Nan             Apple                       Nan           function val   return val     NaN          ----------------------------- -----------   Operator   returns value for objects which have implemented method valueOf  let something         valueOf  function              return 25            console log  something

User · Answer

The   operator returns the numeric representation of the object   So in your particular case  it would appear to be predicating the if on whether or not d is a non-zero number   Reference here   And  as pointed out in comments  here

User · Answer

As explained in other answers it converts the variable to a number  Specially useful when d can be either a number or a string that evaluates to a number  Example  using the addMonths function in the question   addMonths 34 1 true   addMonths  quot 34 quot  1 true    then the  d will evaluate to a number in all cases  Thus avoiding the need to check for the type and take different code paths depending on whether d is a number  a function or a string that can be converted to a number

[javascript] What is the purpose of a plus symbol before a variable?

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