在节点js中，构建模块时如何使用模块中定义的功能？

Question

I defined the function mean, and I want to build a function sd, but at some point I need to use the function mean. But when I use sd from the module it tells me mean is not defined. So what should I do?

module.exports = {

mean: function mean(x){
    var sum = 0;
    var n = x.length;
    for (i=0;i<n;i++){
        sum = sum+x[i];
    }
    var mean = sum/n;
return mean;
},

sd: function sd(x){
    var sum = 0;
    var n = x.length;
    var xmean = mean(x);
    for (i=0;i<n;i++){
        sum = sum + Math.pow(x[i]-xmean,2);
    }
    var sd = Math.sqrt(sum/n);
return sd;
}

};

Answer 1

Call mean as method from this object like

sd: function sd(x){
    var sum = 0;
    var n = x.length;
    var xmean = this.mean(x);
    for (i=0;i<n;i++){
        sum = sum + Math.pow(x[i]-xmean,2);
    }
    var sd = Math.sqrt(sum/n);
return sd;
}