How to find the normal distribution in Javascript?

Question

I'm trying to convert a formula from an Excel spreadsheet into an online calculator, the formula specifically is:

=(NORM.S.DIST(2.5467437 + -1.9344945 *B7^( -0.5),1))^2

The problem I'm encountering is that NORM.S.DIST doesn't appear to exist in any Javascript library that I've found. In researching the problem I did find this solution, but it's a C# based one and I don't know how to convert that into Javascript. How do I approach this problem in Javascript?

Answer 1

EDITED:

This varies from the actual value by less than 0.005:

function cummulativeNormalDist(x) {
    if(x < 2.2) {
        return .1 * x * (4.4 - x);
    } else if(x < 2.6) {
        return .49;
    } else {
        return .50;
    }
}

Source: http://mathworld.wolfram.com/NormalDistributionFunction.html