typeof number + typeof number = NaN?

Question

Why this is NaN in JavaScript?

alert(typeof settings.mouse.x + ' --- ' + typeof getScalePercent((bg_w - a_w)/2, settings.bg.perc_position));
// alerts: number --- number

var pos_x = settings.mouse.x - getScalePercent((bg_w - a_w)/2, settings.bg.perc_position);    
alert(pos_x);
// alerts: NaN

// this syntax because a jQuery plug-in
var getScalePercent = function (value, perc) {
    return value * perc / 100;
}

// settings.mouse.x == 102 basically an integer
// getScalePercent(...) == 10 or 12.0390394028 basically an number

alert(settings.mouse.x + ' (' + typeof settings.mouse.x + ') --- ' + getScalePercent(((bg_w - a_w)/2), settings.bg.perc_position) + '(' + typeof getScalePercent(((bg_w - a_w)/2), settings.bg.perc_position) + ')');
// returns 102 (number) --- 12.000340563 (number)

Where I'm wrong?

What's the value of the variables? And what does getScalePercent do? — ysrb, Feb 05 '12 at 10:30
What are the values of `settings.mouse.x` and the result of the `getScalePercent` function? — Darin Dimitrov, Feb 05 '12 at 10:31
[Can't reproduce](http://jsfiddle.net/ttzz4/) - please post more code. Maybe `bg_w` and/or `a_w` are not defined by the time you call the function. — Shadow The GPT Wizard, Feb 05 '12 at 10:33

score 3 · Accepted Answer · answered Feb 05 '12 at 10:32

3

My guess is that getScalePercent is returning NaN . Since typeof NaN is returning number. Check the function whether it does what you expect to do.

answered Feb 05 '12 at 10:32

ysrb

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there was an error on passing a `undefined` val instead of a `number` in the method `getScalePercent` thank you! – vitto Feb 05 '12 at 10:48

typeof number + typeof number = NaN?

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