JS: Number.prototype.toExponential

number.toExponential(fractionDigits)

Return a string representation of number in exponential notation, with fractionDigits fraction digits.

Example of return string: "3.12e+2". (the “e+2” means multiply by 10^2)

If fractionDigits is undefined, include as many significand digits as necessary to uniquely specify the number (just like in ToString except that in this case the number is always output in exponential notation).

let num = 3.12345;

console.log( 
 num.toExponential ( 1 ) === "3.1e+0" ); // true

console.log( 
 num.toExponential ( 2 ) === "3.12e+0" ); // true

console.log( 
 num.toExponential ( 3 ) === "3.123e+0" ); // true

let num = 12.345;

console.log( 
 num.toExponential ( 1 ) === "1.2e+1" ); // true

console.log( 
 num.toExponential ( 2 ) === "1.23e+1" ); // true

console.log( 
 num.toExponential ( 3 ) === "1.235e+1" ); // true

let num = 0.123;

console.log( 
 num.toExponential ( 1 ) === "1.2e-1" ); // true

console.log( 
 num.toExponential ( 2 ) === "1.23e-1" ); // true

console.log( 
 num.toExponential ( 3 ) === "1.230e-1" ); // true