javascript using the unary-plus and unary-minus operator 一元操作符

新手入门啊，看看就明白了！

  
    

   
     <
   
     script src
   
     =
   
     '
   
     jquery.js
   
     '
   
     ><
   
     /
   
     script>
   
     

   
     ......

   
     <
   
     script
   
     >
   
     

   
     var
   
      a
   
     =
   
     1
   
     ;

   
     var
   
      b
   
     =
   
     '
   
     2
   
     '
   
     ;


   
     //
   
     output number
   
     

   
     console.log(
   
     typeof
   
     (
   
     -
   
     b));
console.log(
   
     typeof
   
     (
   
     +
   
     b));

   
     //
   
     output string
   
     

   
     console.log(
   
     typeof
   
     (b));


   
     //
   
     output 12
   
     

   
     console.log(a 
   
     +
   
      b);


   
     //
   
     output 3
   
     

   
     console.log(a 
   
     +
   
      Number(b));
console.log(a 
   
     +
   
      
   
     +
   
     b);
console.log(a 
   
     -
   
      
   
     -
   
     b);


   
     //
   
     output -1
   
     

   
     console.log(a 
   
     +
   
      
   
     -
   
     b);
console.log(a 
   
     -
   
      
   
     +
   
     b);

   
     <
   
     /
   
     script>