fesf22.md

1. Let x be ? thisNumberValue(this value).
2. Let f be ? ToIntegerOrInfinity(fractionDigits).
3. Assert: If fractionDigits is undefined, then f is 0.
4. If f is not finite, throw a RangeError exception.
5. If f < 0 or f > 100, throw a RangeError exception.
6. If x is not finite, return ! Number::toString(x).
7. Set x to ℝ(x).
8. Let s be the empty String.
9. If x < 0, then
a. Set s to "-".
b. Set x to -x.
10. If x ≥ 1021, then
a. Let m be ! ToString(𝔽(x)).
11. Else,
a. Let n be an integer for which n / 10^f - x is as close to zero as possible. If there are two such n, pick the larger n.
b. If n = 0, let m be the String "0". Otherwise, let m be the String value consisting of the digits of the decimal representation of n (in order, with no leading zeroes).
c. If f ≠ 0, then
i. Let k be the length of m.
ii. If k ≤ f, then
1. Let z be the String value consisting of f + 1 - k occurrences of the code unit 0x0030 (DIGIT ZERO).
2. Set m to the string-concatenation of z and m.
3. Set k to f + 1.
iii. Let a be the first k - f code units of m.
iv. Let b be the other f code units of m.
v. Set m to the string-concatenation of a, ".", and b.
12. Return the string-concatenation of s and m