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如果多个均为false 则内层触发先于外层
var arr = ["a","b""2","3","str"]; var result = ("b" in arr); var result1 = (4 in arr); document.write(result); document.write(result1); 程序运行结果是?
Afalse，true
Btrue,false
Cfalse，false
Dtrue, true

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出自：新疆开放大学javascript程序设计

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