Javascript IRR (Internal rate of return) Formula Accuracy

Question

I\'m using a IRR function in javascript to create calculation a that is done in excel using its own IRR function. The problem is mine is little off and I have no idea why. Here\

Answer 1

Try this.

function NPV(discountRate, cashFlow){
    var npv = 0;
    for(var t = 0; t < cashFlow.length; t++) {
        npv += cashFlow[t] / Math.pow((1+ discountRate),t);
    }
    return npv;
}


function IRR(cashFlow,guess){
    guess = guess ? guess : 0.1;
    var npv;
    var cnt = 0;
    do
    {
        npv = NPV(guess,cashFlow);
        guess+= 0.001;

        cnt++;
    }
    while(npv > 0)

    return guess;
}