How to use switch in JavaScript

Question

I have been trying to make a password generator and I have this code and it is returning "undefined" not a character. The code is supposed to return 16 characters with numbers, lower and upper characters. I want to have this so that I don't have to worry about making my own passwords anymore.

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>PassGen</title>
  <script>
    function getRandomInt(min, max) {
      return Math.floor(Math.random() * (max - min + 1)) + min;
    }

    function num2lett(num) {
      switch (num) {
        case (num > 36):
          return String.fromCharCode(577 + num - 35);
          break;
        case (num > 10 && num < 37):
          return String.fromCharCode(97 + num - 11);
          break;
        case (num == 10):
          return "0";
          break;
        case (num < 10):
          return "" + num;
          break;
      }

    }

    function uuidMake() {
      var uuid = "";
      for (u = 0; u < 16; u++) {
        randNum = getRandomInt(0, 62);
        uuid += num2lett(randNum);
      }
      document.getElementById("password").innerHTML = uuid;
    }
  </script>
  <style>
    @font-face {
      font-family: "uuid_font";
      src: url("Courier Prime Code.ttf") format("TrueType");
    }
    
    body {
      background-color: #262626;
    }
    
    #password {
      font-family: "uuid_font";
      text-align: center;
      font-size: 30px;
      color: #dddddd;
      margin-top: 250px;
    }
  </style>

  <body>
    <p id="password" onclick="uuidMake();">Click Me</p>
  </body>

</html>

user149341 · Accepted Answer · 2017-07-30 06:32:53Z

2

This isn't a good use case for switch. Use if and else statements.

The cases in a switch statement are specific possible values of the expression that you're switching on. For instance, one might write something like:

switch (n) {
    case 1:
        // things to do when n is 1
        break;
    case 3:
    case 4:
        // things to do when n is 3 or 4
        break;
    default:
        // things to do when n is neither 1, 3, nor 4
}

A case statement cannot be a range of values. Using an expression as a case is not recommended, either -- it isn't invalid, but it will probably not do what you expect either.

answered Jul 30, 2017 at 6:32

user149341

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Comments

Milan Chheda · Accepted Answer · 2017-07-30 07:10:40Z

1

You can't use case statements like if else so just use if else condition that will work like as following example.

function getRandomInt(min, max) {
  return Math.floor(Math.random() * (max - min + 1)) + min;
}

function num2lett(num) {
  if (num > 36)
    return String.fromCharCode(577 + num - 35);
  else if (num > 10 && num < 37)
    return String.fromCharCode(97 + num - 11);
  else if (num == 10)
    return "0";
  else if (num < 10)
    return "" + num;
}

function uuidMake() {
  var uuid = "";
  for (u = 0; u < 16; u++) {
    randNum = getRandomInt(0, 62);
    uuid += num2lett(randNum);
  }
  document.getElementById("password").innerHTML = uuid;
}

@font-face {
  font-family: "uuid_font";
  src: url("Courier Prime Code.ttf") format("TrueType");
}

body {
  background-color: #262626;
}

#password {
  font-family: "uuid_font";
  text-align: center;
  font-size: 30px;
  color: #dddddd;
  margin-top: 250px;
}

<p id="password" onclick="uuidMake();">Click Me</p>

What is your algorithm I don't know so I am just converted your algorithm to if else

edited Jul 30, 2017 at 7:10

Milan Chheda

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answered Jul 30, 2017 at 6:32

Sourabh Somani

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2 Comments

osyra42 Over a year ago

Most of this is working, I'm a bit worried about the caps letters though, any idea on how to fix that? I though it was 577 (unicode)

Sourabh Somani Over a year ago

Replace this line first if condition by this line if (num > 36) return String.fromCharCode(65 + num - 35);

Anurag Singh Bisht · Accepted Answer · 2017-07-30 06:32:31Z

1

In the switch block, you have written conditional statements in the case.

You can't use conditional statements in the switch block. Hence in your case none of the case are executing. As you don't have a default block, your function doesn't returns anything, which in case of javascript is undefined. Hence you are getting undefined

answered Jul 30, 2017 at 6:32

Anurag Singh Bisht

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Comments

Jibin.Jay · Accepted Answer · 2017-07-30 07:17:11Z

0

You can alter switch statement to make it work. Pass 'true' in switch and remove parentheses from case condition

switch (true) {
   case num > 36:

answered Jul 30, 2017 at 7:17

Jibin.Jay

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