Nodejs Utililty Methods Array Mean

Array.prototype.mean = function() {
    return !this.length ? 0
        : this.reduce(function(pre, cur, i) {
            return (pre * i + cur) / (i + 1);
            });
console.log( [1,2,3,4,5].mean() );   
console.log( [].mean() );            

Array.prototype.mean = function () {
  var sum = this.reduce(
    function (prev, cur) {
      return prev + cur;
  );
  return sum / this.length;

Array.prototype.mean = function(){ 
  return this.reduce(function(previousMean, currentValue, i){
    return previousMean + (1/(i + 1))*(currentValue - previousMean);
  });
};
Array.prototype.median = function() {
   var values = this;
    values.sort( function(a,b) {return a - b;} );
    var half = Math.floor(values.length/2);
...

Array.prototype.mean = function () {
    var sum = this.reduce(function(previousValue, currentValue) {
        return previousValue + currentValue;
    });
    return sum / this.length;
};

Array.prototype.mean = function() {
    mean = 0;
    for (var i = 0; i < this.length; i++) {
        mean += this[i];
    mean = mean / this.length;
    return mean;
};

Array.prototype.mean = function() {
  var length = this.length;
  return this.total()/length;
};

Array.prototype.mean = function(){
    return this.sum()/this.length;
Array.prototype.sum = function(){
  var ret = this[0];
  for(var i=1;i<this.length;i++){
    ret += this[i]
  return ret;
...

Array.prototype.mean = function() {
  return (this.total()) / (this.length);
Array.prototype.total = function() {
   var finalTotal = this.reduce(function(total, number){
     return total + number;
   }, 0);
   return finalTotal

Array.prototype.mean = function(){
    return this.sum()/this.length;

Array.prototype.mean = function() {
  for ( var b = 0, d = this.length, c = 0; b < d; c += this[b++]) {
  var a = c / d;
  return a
};