JS中数字和字符相加相减问题
<html lang="en">
<head>
<meta charset="utf-8" />
<title></title> </head>
<body>
</body>
</html>
<script type="text/javascript">
var a = 100;
var b = "100";
alert(b- a);
alert(typeof (b- a));
alert(a + b - a);
alert(typeof (a + b - a));
alert(a + b);
alert(typeof (a + b));
alert(a + b - b);
alert(typeof (a + b - b));
alert(a + b - b - b);
alert(typeof (a + b - b - b));
alert(true + 1);//2 ,true被转化为1,false转化为0
alert(true + "1");//true1 , true被转化为字符串“true”
</script>
执行结果
0
number
100000
number
100100
string
100000
number
99900
number
2
true1
由此可知道JS在进行这种运算时 仅仅会在2个值相加时优先推断为string类型 其它情况下(比如“-”。“*”。“/”)都默觉得number型运算。!
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