The use of the reduce () method in JavaScript-basic knowledge

The JavaScript array reduce () method applies a function to two values (from left to right) of the array at the same time to reduce to a value.
Grammar

Array.reduce (callback[, InitialValue]);

The following are the details of the parameters:

• Callback: function executes each value in the array
• InitialValue: The first invocation of an object as the first parameter callback uses the

return value:

Returns the reduction of an array by a single value
Compatibility :

This approach is a JavaScript extension to the ECMA-262 standard; Therefore it may not exist in other implementations of the standard. To make it work, you need to add the top of the following scripting code:

if (! Array.prototype.reduce)
{
 Array.prototype.reduce = function (Fun/*, initial*/)
 {
  var len = This.length;
  if (typeof fun!= "function")
   throw new TypeError ();

  No value to return if no initial value and a empty array
  if (len = 0 && arguments.length = 1)
   throw New TypeError ();

  var i = 0;
  if (arguments.length >= 2)
  {
   var rv = arguments[1];
  }
  else
  {
   do
   {
    if (i) {
     RV = this[i++];
     break;

    If array contains no values, no initial value to return
    if (++i >= len)
     throw new TypeError ();
   } While
   (true);
  }

  for (; i < Len; i++)
  {
   if (i)
    RV = Fun.call (null, RV, this[i], I, this);
  }

  return RV;}
 ;
}

Example:

This will produce the following results:

Total Is:6