atoi function

int atoi(String s)

String to Integer (Atoi): Converts a string to an integer, handling optional +/- and whitespace. Converts a string s to an integer, handling optional +/- and whitespace (Atoi).

Ignores leading whitespace, parses an optional sign, and reads digits until a non-digit is found.

Returns the integer value represented by s.

Example:

print(atoi("   -42")); // -42
print(atoi("4193 with words")); // 4193

Implementation

int atoi(String s) {
  int i = 0, n = s.length, sign = 1, result = 0;
  while (i < n && s[i] == ' ') {
    i++;
  }
  if (i < n && (s[i] == '-' || s[i] == '+')) sign = s[i++] == '-' ? -1 : 1;
  while (i < n && s[i].codeUnitAt(0) >= 48 && s[i].codeUnitAt(0) <= 57) {
    result = result * 10 + (s[i++].codeUnitAt(0) - 48);
  }
  return sign * result;
}