JavaScript, Switch Statement

Question

A Little stuck on this problem, I think I have the switch statement not in working condition. This is the prompt:

1) Use a sentinel while loop that only exits when the number zero (0) is read.
2) Inside the sentinel while loop
2.a) Read a musketeer number. You can assume this is a unique serial number printed on the musketeer's uniform.
2.b) Look up the table below, find a matching name with a JavaScript switch statement, and then save the name to a variable.
2.c) Print out the matching name with either innerHTML or document.write(), with proper prompt.
2.d) Give an error message if no match can be found in the table below for a given musketeer number.

Now here was my code:

var idnum;
var input;

input = window.prompt("Enter a Uniform ID (0 to quit): ");
idnum = parseInt(input);

function getData(rNum, cNum) {
  var table = document.getElementById('musketeer');
  var rowElem = table.rows[rNum];
  var tdValue = rowElem.cells[cNum].innerHTML;
  var match = parseInt(tdValue);
  return match;
}

while (idnum != 0) {
  switch (idnum) {
    case 1001 === getData(2, 0):
      document.writeln("That is Musketeer D'Artagnan");
      break;
    case 2034 === getData(3, 0):
      document.writeln("That is Musketeer Athos");
      break;
    case 2178 === getData(4, 0):
      document.writeln("That is Musketeer Aramis");
      break;
    case 1091 === getData(5, 0):
      document.writeln("That is Musketeer Porthos");
      break;
    default:
      document.writeln("That ID does not match a musketeer.");
  }
}

<html>

<head>
  <title>Lab 9</title>
</head>

<body>
  <table id='musketeer' border=1 cellpadding=0 cellspacing=0>
    <tr>
      <td><strong>Musketeer Number</strong></td>
      <td><strong>Musketeer Name</strong></td>
    </tr>
    <tr>
      <td>1001</td>
      <td>D'Artagnan</td>
    </tr>
    <tr>
      <td>2034</td>
      <td>Athos</td>
    </tr>
    <tr>
      <td>2178</td>
      <td>Aramis</td>
    </tr>
    <tr>
      <td>1091</td>
      <td>Porthos</td>
    </tr>
  </table>
</body>

</html>

I really fail to see why you need a switch statement in your case. A tip might be is idnum a boolean value? if not, you will end up in the default branch at all times. Why not store the data in a Set, so you can do a simple look up against the set? btw, what a horrible schoolwork task are they giving you, prompts, while loops, document.write, that teacher should really refresh on what js can do... — Icepickle
– Icepickle, Commented Feb 21, 2018 at 1:10
If getData works you could try something like switch(idnum) { case getData(2,0): ... break; case getData(3,0): ... break; ...}. — jonasfh
– jonasfh, Commented Feb 21, 2018 at 1:18
Not sure what are you doing, but you are comparing idnum to Boolean values in the case statements... — Akxe
– Akxe, Commented Feb 21, 2018 at 1:23

Matt · Accepted Answer · 2018-02-21 01:43:42Z

That's not how a switch statement works, you can't compare a case value to something. You should write it like this:

switch(number) {
  case 1:
    // do something
    break;
  case 2:
    // do something else
    break;
  default:
    // do default
    break;
}

As for your program, your prompt should be inside the while loop so it repeatedly asks for a number until the user wants to quit.

Something like this:

var input = window.prompt("Enter a Uniform ID (0 to quit): ");
var idnum = parseInt(input);

while(number != 0) {
  // use the number to perform a lookup
  var name;
  switch(idnum) {
     case 1001:
        // return the name NOT THE NUMBER
        name = getData(2, 1);
        break;
     case 2034:
        name = getData(3, 1);
        break;
     default:
        name = "";
        break;
  }

  // print out the name, or error (or you can write it to the page)
  if(name != "") {
     console.log("That is Musketeer " + name);
  } else {
     console.log("No Musketeer found with Uniform ID " + idnum);
  }

  // prompt for another number
  input = window.prompt("Enter a Uniform ID (0 to quit): ");
  idnum = parseInt(input);
}

jonasfh · Accepted Answer · 2018-02-21 02:00:24Z

0

To dynamically solve this, you should loop over the table, compare the input to the first column, and if that matches display the result from the second column, like

  var table = document.getElementById('musketeer');
 for(i=0; i<table.rows.length; i++) {
   if(idnum==table.rows[i].cells[0].innerHtml){
     alert("That is Musketeer " + table.rows[i].cells[1].innerHtml);
  } 
 }

edited Feb 21, 2018 at 2:00

answered Feb 21, 2018 at 1:49

jonasfh

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Comments

Damsith Karunaratna · Accepted Answer · 2018-02-21 02:05:41Z

0

case 1001 === getData(2, 0):

is not valid. It literally means "the case when 1001 is the same as getData(2,0)". (which it's either true or false).

try,

case getData(2, 0):

this sets the value from your table as one of the switch cases. see this working example

edited Feb 21, 2018 at 2:05

answered Feb 21, 2018 at 1:44

Damsith Karunaratna

617 bronze badges

1 Comment

Caden Raymond Over a year ago

Thanks for the feedback!

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