Javascript Array reduce(process, initial)

Array.prototype.reduce = function(process, initial) {
  var reduction;/* w w  w  .j a va  2 s.c  o  m*/
  if(initial === undefined){
    reduction = this[0];
    for(var i=1;i<this.length;i++){
        reduction = process(reduction,this[i])
    }
  }
  else{
  reduction = initial;
  for(var i=0;i<this.length;i++){
        reduction = process(reduction,this[i])
    }
  }
  return reduction
}

Array.prototype.reduce = function(process, initial) {
  var value = initial;
  for (var i = 0; i < this.length; i++) {
    if( ( i === 0 ) && ( value === undefined || value === null ))
    {//from w w w .j  av  a  2 s .co  m
        value = this[0];
        continue;
    }
    value = process( value, this[i] );
  }
  return value;
};

Array.prototype.reduce = function(process, initial) {
    const initVal = typeof this[0] === 'string' ? '' : 0;
    initial = initial || initVal; //w  w w .j av a2 s .co  m
    for (let i=0;i<this.length;i++){
        initial = process(initial,this[i])
    }
    return initial;
}

Array.prototype.reduce = function(process, initial) {

  // how to access an array which invokes a function
  // they give us the actual function
  // we just have to set the initial to the first parm of the function
  // and call that function each time on the second parm which represent each elem in the array
  // need to be able to access elem of te array that func with 'this'
  var total;/*from w  w  w  .  j  a  v a 2 s .c o  m*/

    if(initial) {
      total = initial;
    } else {
      total = this.shift(); // had to remove the first element in order to avoid
                            // duplicates in strings
    }

    for(var i = 0; i < this.length; i++) {
      total = process(total, this[i]);
    }
    return total;
}