toExponential() function returns the exponential notation of a number.
var nm = 10000; nm.toExponential(); //1e+4
var nm = 1000.433; nm.toExponential(); //1.000433e+3
Use toPrecision() to round the decimals.
var nm = 54326 * 432211; //23480294786 nm.toExponential(); //2.3480294786e10 nm.toExponential(3);//2.348e10