JavaScript Operator: increment
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In JavaScript,
the ++ operator is
the (unary) arithmetic operator for incrementing, i.e. adding one to the variable.
There are technically two different increment operators, the prefix one, and
the postfix one.
For example, if x is 8
then the statement y = ++x
results in x being incremented
to 9 and then y assigned this
value (i.e. is assigned 9).
However, the statement y = x++
involves y being assigned the
value of x (i.e. 8) and x
then being incremented to 9.
For code clarity, some
commentators suggest using the statements x
= x + 1; y = x; instead of y =
++x and y = x; x = x + 1;
instead of y = x++.
EXAMPLE:
HTML USED IN THIS EXAMPLE:
<!DOCTYPE html>
<html> <!-- Copyright (c) Nematrian Limited 2018 -->
<head>
<style>table,th,tr,td {border: 1px solid black;
border-collapse: collapse;}</style>
</head>
<body>
JavaScript arithmetric increment operator (prefix and postfix)<br><br>
<table>
<tr>
<th>Example</th>
<th>Resulting value of <code>x</code></th>
<th>Resulting value of <code>y</code></th>
</tr>
<tr>
<td><code id="IncrementPrefixExample"></code></td>
<td><code id="IncrementPrefixx"></code></td>
<td><code id="IncrementPrefixy"></code></td>
</tr>
<tr>
<td><code id="IncrementPostfixExample"></code></td>
<td><code id="IncrementPostfixx"></code></td>
<td><code id="IncrementPostfixy"></code></td>
</tr>
</table>
<script>
document.getElementById("IncrementPrefixExample").innerHTML =
'var x = 8;<br>' +
'var y = ++x;';
var x = 8; var y = ++x;
document.getElementById("IncrementPrefixx").innerHTML = x;
document.getElementById("IncrementPrefixy").innerHTML = y;
document.getElementById("IncrementPostfixExample").innerHTML =
'var x = 8;<br>' +
'var y = x++;';
x = 8; y = x++;
document.getElementById("IncrementPostfixx").innerHTML = x;
document.getElementById("IncrementPostfixy").innerHTML = y;
</script>
</body>
</html>
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