標籤：alert 結果 type charset 情況 ext 字元 typeof 布爾類型
JS中數字和字元相加相減問題<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被轉化為1，false轉化為0
alert（true + "1"）;//true1 , true被轉化為字串“true”</script>
執行結果
0
number
100000
number
100100
string
100000
number
99900
number
2
true1
由此可知道JS在進行這種運算時 僅僅會在2個值相加時優先推斷為string類型 其它情況下(比如“-”。“*”。“/”)都默覺得number型運算。！
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js面試題--------JS中數字和字元,布爾類型相加相減問題
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