find closest number in the sequence (1, 5, 10, 50, 100, 500, 1000, ...) that generates less than "n" steps

gistfile1.js

//
// find closest number in the sequence (1, 5, 10, 50, 100, 500, 1000, ...)
// that generates less than "n" steps
// ---
// useful for subdividing charts and any other things that requires a scale
// that follows reasonable numbers
//
function getStepSize(val, maxNSteps) {
    var nSteps;
    var stepSize = 1;
    var count = 0;

    do {
        if (count) {
            stepSize *= (count % 2)? 5 : 2;
        }
        nSteps = Math.ceil(val / stepSize);
        count += 1;
    } while (nSteps > maxNSteps);

    return stepSize;
}


// example
// -------

getStepSize(1000, 2);   // 500
getStepSize(1000, 5);   // 500
getStepSize(1000, 10);  // 100
getStepSize(1000, 20);  // 50
getStepSize(1000, 50);  // 50
getStepSize(1000, 150); // 10

I was looking for something like this a while back and couldn't find anything because I had no idea what terms to search. Given two bounds, the minimum and maximum values that need to be plotted, I wanted to get a reasonable list of round numbers on which to place the gridlines. After much trial and error I came up with a sloppy but serviceable function and called it "gridlines." https://gist.github.com/3137681