limit the exponential notation decimal place to 4 in javascript

问题

How to limit the decimal place to 4 in javascript with this type of values? the e is the exponent since I am using power of ten values. toFixed() doesn't seem to work.

1.0531436913408342e-7
-5.265718456704172e-7
8.425149530726674e7

回答1:

Try:

   Math.round(val*10000)/10000

回答2:

Try this method: value.toPrecision(1 + 4) for 4 decimal digits.

回答3:

use the force, Luke!

There's actually a javascript method specifically for limiting the number of decimal places to show in exponential notation:
*numObj*.toExponential([*fractionDigits*])

Using your example numbers you get:
1.0531436913408342e-7.toExponential(4) // returns 1.0531e-7 -5.265718456704172e-7.toExponential(4) // returns -5.2657e-7 8.425149530726674e7.toExponential(4) // returns 8.4251e+7

Quote from MDN:

Returns a string representing a Number object in exponential notation with one digit before the decimal point, rounded to fractionDigits digits after the decimal point

回答4:

You can use Math.round();

Using Math.round(x) will round up or down to the nearest integer (using the classic .5 rule).

You can pass in your own criteria and have it do decimal places. The link below has examples for 1, 2, and 3 decimal places.

Here is the link

来源：https://stackoverflow.com/questions/7269894/limit-the-exponential-notation-decimal-place-to-4-in-javascript