Javascript Regex into Rust regex

I have a Javascript regex for password validation:

// Validates password with
// — No white spaces
// — At least one upper case English letter, (?=.*?[A-Z])
// — At least one lower case English letter, (?=.*?[a-z])
// — At least one digit, (?=.*?[0-9])
// — Minimum eight in length .{8,} (with the anchors)

const passwordRegex = /^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9]).{6,10}$/;

I am trying to translate it into Rust regex using regex library; but it seems that it doesn’t support lookahead: https://docs.rs/regex/latest/regex/

use regex::Regex;

pub fn validate_password(string: &str) -> bool {
  let regex_no_whitespaces = Regex::new(r"^\s*\S+\s*$").unwrap();
  let regex_password = Regex::new(r"^(?=.*?[A-Z])(?=.*?[a-z])(?=.*?[0-9]).{6,10}$").unwrap();
  let password_valid = regex_password.is_match(&string);
  let password_has_no_whitespaces = regex_no_whitespaces.is_match(&string);
  let is_valid = password_valid && password_has_no_whitespaces;

  return is_valid;
}

What is the common way to validate a string with multiple conditions without a lookahead?

EDIT: it is possible to do it using Regex, here a version in the playground: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=c6f69f5018e38677af1624a7bfcd186c. But the version provided by @sirdarius is way cleaner.

>Solution :

Here is a solution that does not use regular expressions.

fn is_password_valid(s: &str) -> bool {
    let mut has_whitespace = false;
    let mut has_upper = false;
    let mut has_lower = false;
    let mut has_digit = false;

    for c in s.chars() {
        has_whitespace |= c.is_whitespace();
        has_lower |= c.is_lowercase();
        has_upper |= c.is_uppercase();
        has_digit |= c.is_digit(10);
    }

    !has_whitespace && has_upper && has_lower && has_digit && s.len() >= 8
}

Playground link