Looking for a WORKING Bollinger Bands Indicator

Code:

var periodbb = 20;



strat.init = function() {



this.addIndicator('bb', 'BB', {optInTimePeriod: periodbb } );

strat.check = function(candle) {

 var BB = this.indicators.bb;



console.log(BB)

Code:

// required indicators: SMA;

// Bollinger Bands implementation;

var SMA = require('./SMA.js');

var Indicator = function(BBSettings) {

    this.input = 'price';

    this.settings = BBSettings;   

    this.center = new SMA(this.settings.TimePeriod);



    this.lower=0;

    this.middle=0;

    this.upper=0;

}



Indicator.prototype.calcstd = function(prices, Average)

{

    var squareDiffs = prices.map(function(value){

        var diff = value - Average;

        var sqr = diff * diff;

        return sqr;

    });



    var sum = squareDiffs.reduce(function(sum, value){

        return sum + value;

    }, 0);



    var avgSquareDiff = sum / squareDiffs.length;



    return Math.sqrt(avgSquareDiff);

}



Indicator.prototype.update = function(price) {

    this.center.update(price);



    this.middle = this.center.result;

    var std = this.calcstd(this.center.prices, this.middle);



    this.lower = this.middle - this.settings.NbDevDn * std;

    this.upper = this.middle + this.settings.NbDevUp * std;

}



module.exports = Indicator;