How to apply a function to two values of an array simultaneously from right to left?-HTML Tutorial-php.cn

How to apply a function to two values of an array simultaneously from right to left?

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Release： 2023-09-16 23:25:08

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How to apply a function to two values of an array simultaneously from right to left?

Use the reduceRight() method in JavaScript to simultaneously apply a function to two values of an array in a right-to-left manner to reduce it to a single value.

The following are the parameters:

callback − Function executed on each value of the array.
initialValue − The object used as the first parameter of the callback

Example

You can try running the following code to understand how to use reduceRight() method in JavaScript:

<html>
   <head>
      <title>JavaScript Array reduceRight Method</title>
   </head>
   <body>
      <script>
         if (!Array.prototype.reduceRight)
         {
            Array.prototype.reduceRight = function(fun /*, initial*/)
            {
               var len = this.length;
               if (typeof fun != "function")
               throw new TypeError();
             
               // no value to return if no initial value, empty array
               if (len == 0 && arguments.length == 1)
               throw new TypeError();
               var i = len - 1;
               if (arguments.length >= 2)
               {
                  var rv = arguments[1];
               } else {
                  do
                  {
                     if (i in this)
                     {
                        rv = this[i--];
                        break;
                     }
                     // if array contains no values, no initial value to return
                     if (--i < 0)
                     throw new TypeError();
                  }
                  while (true);
                  }
                  for (; i >= 0; i--)
                  {
                     if (i in this)
                     rv = fun.call(null, rv, this[i], i, this);
                  }
               return rv;
            };
         }
         var total = [0, 1, 2, 3].reduceRight(function(a, b) { return a + b; });
         document.write("total is : " + total );
      </script>
   </body>
</html>

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