You can use this method to get a string representing the number in exponential notation:

new Number(10).toExponential() //1e+1 (= 1 * 10^1)
new Number(21.2).toExponential() //2.12e+1 (= 2.12 * 10^1)

You can pass an argument to specify the fractional part digits:

new Number(21.2).toExponential(1) //2.1e+1
new Number(21.2).toExponential(5) //2.12000e+1

Notice how we lost precision in the first example.