Javascript Array mean()

Array.prototype.mean = function() {
    return !this.length ? 0
        : this.reduce(function(pre, cur, i) {
            return (pre * i + cur) / (i + 1);
            });//from w  w  w.j av  a  2s.  c  om
    }

alert( [1,2,3,4,5].mean() );   // 3
alert( [].mean() );            // 0

Array.prototype.mean = function(){ 
 return this.reduce(function(previousMean, currentValue, i){
  return previousMean + (1/(i + 1))*(currentValue - previousMean);
 });/*from  w  w  w.j a  v  a 2  s. c  o m*/
};

Array.prototype.mean = function () {
    var sum = this.reduce(function(previousValue, currentValue) {
        return previousValue + currentValue;
    });/*from   w ww . ja va  2 s.  c o m*/

    return sum / this.length;
};

Array.prototype.mean = function() {
    mean = 0;//from  w w w  .ja v a 2  s . c  om
    for (var i = 0; i < this.length; i++) {
        mean += this[i];
    }
    mean = mean / this.length;
    return mean;
};

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


Array.prototype.median = function() {
    var middle = Math.floor(this.length / 2);
    var evenMiddle = (this[middle-1] + this[middle]) / 2;
    if (this.length % 2 == 0) {
        return evenMiddle;
    } else {
        return this[middle];
    }
}

Array.prototype.mode = function() {
    freq = {};
    for (var i = 0; i < this.length; i++) {
        var curEl = this[i];
        freq[curEl] ? freq[curEl]++ : freq[curEl] = 1;
    }

    var max = 1;
    for (key in freq) {
        if (freq[key] > max) {
            max = freq[key];
            maxObj = {};
            maxObj[key] = max;
        }
    }
    return maxObj;
}