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加算子と減算子

加算子はインクリメント演算子、減算子はデクリメント演算子ともよばれ、主にループ処理とセットで使用されます。

JavaScript

加算子

変数を1度使用した後に1繰り上げる

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 0;

document.getElementById("first").innerHTML =  kensu++;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

01 

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 0;

document.getElementById("first").innerHTML = kensu;

document.getElementById("second").innerHTML = kensu += 1;
</script>
</html>

01

変数を使用する前に1繰り上げる

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 0;

document.getElementById("first").innerHTML = ++kensu;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

11 

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 0;

document.getElementById("first").innerHTML = kensu += 1;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

11

減算子

変数を1度使用した後に1繰り下げる

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 1;

document.getElementById("first").innerHTML = kensu--;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

10 

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 1;

document.getElementById("first").innerHTML = kensu;

document.getElementById("second").innerHTML = kensu -= 1;
</script>
</html>

10

変数を使用する前に1繰り下げる

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 1;

document.getElementById("first").innerHTML = --kensu;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

00 

<!DOCTYPE HTML>
<html lang="ja-JP">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<span id="first"></span><span id="second"></span>
</body>
<script type="text/javascript">
var kensu = 0;

document.getElementById("first").innerHTML = kensu -= 1;

document.getElementById("second").innerHTML = kensu;
</script>
</html>

00

PHP

加算子

変数を1度使用した後に1繰り上げる

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 0;

echo $kensu++;

echo $kensu;
?>

01 

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 0;

echo $kensu;

echo $kensu += 1;
?>

01

変数を使用する前に1繰り上げる

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 0;

echo ++$kensu;

echo $kensu;
?>

11 

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 0;

echo $kensu + =1;

echo $kensu;
?>

11

減算子

変数を1度使用した後に1繰り下げる

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 1;

echo $kensu--;

echo $kensu;
?>

10 

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 1;

echo $kensu;

echo $kensu -= 1;
?>

10

変数を使用する前に1繰り下げる

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 1;

echo --$kensu;

echo $kensu;
?>

00 

<?php
header("Content-type: text/plain; charset=utf-8");

$kensu = 1;

echo $kensu -= 1;

echo $kensu;
?>

00

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