JavaScript function to generate randomized passwords

genPassword.js

/**
 * Generates a random password for a given length and complexity
 * @param  {int} len          number of characters in the password
 * @param  {boolean} upper    toggle to include uppercase letters
 * @param  {boolean} number   toggle to include numeric digits
 * @param  {boolean} special  toggle to include special characters
 * @param  {boolean} space    toggle to include non-breaking space
 * @return {string}           password including minimum 1 character of each complexity
 */
function genPassword(len,upper,number,special,space) {
    var lower_chars = "abcdefghijklmnopqrstuvwxyz";
    var upper_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    var numbers = "1234567890";
    var special_chars = "!@#$%^&*";

    var password = lower_chars[Math.floor(Math.random() * lower_chars.length)];;
    var complexity = [1,0,0,0,0];
    
    if(upper === true) {
        password += upper_chars[Math.floor(Math.random() * upper_chars.length)];
        complexity[1] = 1;
    }
    if(number === true) {
        password += numbers[Math.floor(Math.random() * numbers.length)];
        complexity[2] = 1;
    }
    if(special === true) {
        password += special_chars[Math.floor(Math.random() * special_chars.length)];
        complexity[3] = 1;
    }
    if(space === true) {
        password += " ";
        complexity[4] = 1;
    }
    
    for(var i=password.length; i<len; i++) {
      do {
         var char_type = Math.floor(Math.random() * 5);
      } while(complexity[char_type] != 1);
        switch(char_type) {
            case 0:
                password += lower_chars[Math.floor(Math.random() * lower_chars.length)];
                break;
            case 1:
                password += upper_chars[Math.floor(Math.random() * upper_chars.length)];
                break;
            case 2:
                password += numbers[Math.floor(Math.random() * numbers.length)];
                break;
            case 3:
                password += special_chars[Math.floor(Math.random() * special_chars.length)];
                break;
            case 4:
                password += " ";
                break;
        }
    }
    
    function scramble(a){a=a.split("");for(var b=a.length-1;0<b;b--){var c=Math.floor(Math.random()*(b+1));d=a[b];a[b]=a[c];a[c]=d}return a.join("")}
    
    return scramble(password);
}

//console.log(genPassword(25,true,false,true,false));