JavaScript check if string is empty during onClick function

Question

Can anyone advise me what is wrong with the empty String check in the JavaScript below.

It works fine if I remove the line of code which checks for empty String, but I would like to display "Nothing selected" if the selection is empty.

<html>
  <script language="JavaScript">
  <!--
  function update()
  {
    var selection = "";
    var empty = "";
    if (document.form1.TeaName.checked)    selection += "Tea<br>";
    if (document.form1.CoffeeName.checked) selection += "Coffee<br>";
    if (document.form1.EggsName.checked)   selection += "Eggs<br>";
    if (document.form1.BaconName.checked)  selection += "Bacon<br>";
    if (selection.equals(empty)) selection = "Nothing selected.";
    document.getElementById("currentSelection").innerHTML = selection;
  }
  -->
  </script>
  <body>
    <form name="form1">
      <div id="container" style="width:100%">
        <div id="left" style="float:left; width: 30%;">
          <h3>List 1</h3>
          <input type="checkbox" onClick="update()" name="TeaName"    value="Tea">Tea<br>
          <input type="checkbox" onClick="update()" name="CoffeeName" value="Coffee">Coffee<br>
        </div>
        <div id="middle" style="float:left; width: 30%;">
          <h3>List 2</h3>
          <input type="checkbox" onClick="update()" name="EggsName"  value="Eggs">Eggs<br>
          <input type="checkbox" onClick="update()" name="BaconName" value="Bacon">Bacon<br>
        </div>
        <div id="right" style="float:left; width: 30%;">
          <h3>Currently selected</h3>
          <p id="currentSelection">Please make a selection.</p>
        </div>
      </div>
    </form>
  </body>
</html>

Thank you for your time,

James

Amit · Accepted Answer · 2015-11-05 23:44:25Z

3

There's no such method equals. Don't complicate things:

if (selection.length === 0) selection = "Nothing selected.";

answered Nov 5, 2015 at 23:44

Amit

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Comments

Yalin · Accepted Answer · 2015-11-05 23:48:04Z

2

replace this row:

 if (selection.equals(empty)) selection = "Nothing selected.";

with this:

 if (selection == "" ) selection = "Nothing selected.";

answered Nov 5, 2015 at 23:48

Yalin

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Payson · Accepted Answer · 2015-11-05 23:51:41Z

0

Try this

if(!selection) selection="Nothing selected.";

answered Nov 5, 2015 at 23:51

Payson

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MDJ · Accepted Answer · 2015-11-05 23:54:47Z

0

There is no equals function in javascript, you either have to check with the length or a simple === operator

if (selection.length<= 0) selection = "Nothing selected.";

               (OR)

if(selection === "") selection  = "Nothing selected";

              (OR)

selection=(selection.length > 0) ? selection : "Nothing selected";

The function equals you have used should be related to some javascript library or framework.

answered Nov 5, 2015 at 23:54

MDJ

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user2575725 · Accepted Answer · 2015-11-05 23:55:44Z

0

You can simply have default text and skip the last check.

var selection = "Nothing selected."; //default text
// your rest of the code.

OR

Last check can be done as

selection = selection || "Nothing selected.";

answered Nov 5, 2015 at 23:55

user2575725

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