JavaScript Number.toLocaleString() with 4 digits after separator
You may use second argument to provide some options. In your case, with default locale:
number.toLocaleString(undefined, { minimumFractionDigits: 4 })
I found that
var number = 49.9712;
number.toLocaleString( { minimumFractionDigits: 4 })
gave the result of "49.971"
In order to actually get the 4 decimal place digits, I did this:
number.toLocaleString(undefined, { minimumFractionDigits: 4 })
Also filling in a country code worked:
number.toLocaleString('en-US', { minimumFractionDigits: 4 })
In both cases I got 49.9712 for the answer.