CODEWITHSUNDEEP
javascriptboolean-logicboolean-expression
qb1234
qb1234

Reputation: 145

JavaScript if statement always returns true

corresponding html:

<html>
<title></title>
<head>

</head>
<body>
<FORM NAME="Calculator">
<TABLE BORDER=4>
<TR>
<TD>
<input type="text"   name="Input" Size="22" value="">
<input type="text" name="notepad" value="">
<br>
</TD>
</TR>
<TR>
<TD>
<INPUT TYPE="button" NAME="one"   VALUE="  1  " class ="digit" >
<INPUT TYPE="button" NAME="two"   VALUE="  2  " class ="digit" >
<INPUT TYPE="button" NAME="three" VALUE="  3  " class ="digit" >
<INPUT TYPE="button" NAME="plus"  VALUE="  +  " class ="operand">
<br>
<INPUT TYPE="button" NAME="four"  VALUE="  4  " class ="digit">
<INPUT TYPE="button" NAME="five"  VALUE="  5  " class ="digit">
<INPUT TYPE="button" NAME="six"   VALUE="  6  " class ="digit">
<INPUT TYPE="button" NAME="minus" VALUE="  -  " class="operand">
<br>
<INPUT TYPE="button" NAME="seven" VALUE="  7  " class ="digit">
<INPUT TYPE="button" NAME="eight" VALUE="  8  " class ="digit">
<INPUT TYPE="button" NAME="nine"  VALUE="  9  " class ="digit">
<INPUT TYPE="button" NAME="times" VALUE="  x  " class ="operand">
<br>
<INPUT TYPE="button" NAME="clear" VALUE="  c  " class ="special">
<INPUT TYPE="button" NAME="zero"  VALUE="  0  " class ="digit">
<INPUT TYPE="button" NAME="Execute"  VALUE="  = " class ="solve">
<INPUT TYPE="button" NAME="div"   VALUE="  /  " class ="operand">
<br>
</TD>
</TR>
</TABLE>
</FORM>

<script type = "text/javascript" src="C:\Users\Quonn\Desktop\QBJS\calculatorjs.js">
</script>
</body>
</html>

javascript:

document.onclick = function(x) {
  var info = x.target;
  if (info.className === "digit" || "operand")
  {
    addDigit();
  }
  else {
    math();
  }
}

function addDigit() {
  alert("x");
}

function math() {
  alert("y");
}

x is passed in from button clicks on a calculator. The if statement returns as true even when info.className is something other than digit/operand. What do i need to change in my if statement to make it return false?

Upvotes: 1

Views: 2329

Answers (3)

jahroy
jahroy

Reputation: 22692

You're not using the || operator correctly.

The || operator is used to OR two values. It appears between the two values.

From your example:

FIRST it checks the left side of your condition:

info.className === "digit"

If true, the || operator returns true (it doesn't evaluate the right side).

Otherwise it evaluates the right side of your condition:

"operand"

This will ALWAYS evaluate to true, because the string "operand" does NOT equal a falsey value.

To fix this, you need to use the correct expression on both sides of the || operator:

if (info.className === "digit" || info.className === "operand") {
    alert("Yay");
}

Upvotes: 4

twinlakes
twinlakes

Reputation: 10228

a string interpreted as a boolean will always return true.

if (info.className === "digit" || "operand") should be if (info.className == "digit" || info.className == "operand")

Upvotes: 0

orip
orip

Reputation: 75427

if (info.className === "digit" || info.className === "operand")

Upvotes: 1

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