请考虑以下代码片段:
> a = [1, undefined, undefined, undefined, 3]
[1, undefined, undefined, undefined, 3]
> b = [1,,,,3]
[1, undefined × 3, 3]
> 1 in a
true
> 1 in b
false
我是不是遗漏了什么?根据我在数组中定义undefined
元素的方式,in
运算符的行为似乎有所不同。
发布于 2015-11-03 19:36:02
//-1 means not in the list
//['a','b','c'].indexOf('a') is return index if not find in the list then it give -1.
if(['a','b','c'].indexOf('d') == -1)
{
console.log('yes it -1')
}
https://stackoverflow.com/questions/22448330
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