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Last Update 2019/12/25


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、

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>