Last Update 2009/03/29
TOP - JavaScript - 演算子 - 代入演算子
代入演算子"="は、右辺値(式)を左辺値(変数・配列)に代入します。
"演算子" + "=" の形式をとる代入演算子は、演算の対象となる右辺の変数を a、左辺の値を b とした場合、
"演算子" + "=" の形式をとる代入演算子は、演算の対象となる右辺の変数を a、左辺の値を b とした場合、
a "演算子"= b
と記述されるものは
a = a "演算子" b
と記述したものと同様の結果となります。
(例)
<SCRIPT type="text/javascript">
<!--
function btnclick()
{
var s = "";
var a = 5;
a += 3;
s = s + "a = 5 → a += 3 → " + a + "\n";
a = "a";
a += "b";
s = s + 'a = "a" → a += "b" → ' + a + "\n";
a = 5;
a -= 3;
s = s + "a = 5 → a -= 3 → " + a + "\n";
a = 5;
a *= 3;
s = s + "a = 5 → a *= 3 → " + a + "\n";
a = 10;
a /= 2;
s = s + "a = 10 → a /= 2 → " + a + "\n";
a = 20;
a %= 7;
s = s + "a = 20 → a %= 7 → " + a + "\n";
a = 2;
a &= 2;
s = s + "a = 2 → a &= 2 → " + a + "\n";
a = 3;
a |= 4;
s = s + "a = 3 → a |= 4 → " + a + "\n";
a = 7;
a ^= 3;
s = s + "a = 7 → a ^= 3 → " + a + "\n";
a = 4;
a <<= 1;
s = s + "a = 4 → a <<= 1 → " + a + "\n";
a = 4;
a >>= 1;
s = s + "a = 4 → a >>= 1 → " + a + "\n";
a = 4;
a >>>= 1;
s = s + "a = 4 → a >>>= 1 → " + a + "\n";
alert(s);
}
//-->
</SCRIPT>