why you should basically never use the Number constructor

gistfile1.js

var n = new Number(x); // where x is a global storing an incrementer
 
function doMath(a){
    if (typeof a == "number") {
        return a + x;
    }
}

doMath(n);

number-constructors.js

var n = new Number(1);
alert(n);               // 1
typeof n;               // object
n instanceof Number;    // true
 
var nn = 1;
alert(nn);              // 1
typeof nn;              // number
n instanceof Number;    // false
 
n == nn;                // true
 
typeof n == typeof nn;  // false
 
n++;
nn++;
alert(n);               // 2
alert(nn);              // 2
 
n == nn;                // true
 
typeof n;               // number
typeof nn;              // number
typeof n == typeof nn;  // true

@see http://blog.founddrama.net/2010/07/why-you-should-basically-never-use-the-number-constructor/