在 Javascript 中检查未定义
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Checking for Undefined in Javascript
提问by Krishnan
I was following the below logic to check if a variable is undefined or not:
我遵循以下逻辑来检查变量是否未定义：
if (variable==undefined){
////implementation
}
But found that for some cases it did not function as expected. So, tried this approach,
但是发现在某些情况下它没有按预期运行。所以，尝试了这种方法，
if(typeof(variable) == "undefined"){
/////implementation
}
So which one is most reliable?
那么哪个最靠谱呢？
采纳答案by Asaph
Your second way is the most reliable but you don't need the parenthesis for the typeofoperator. See this question.
您的第二种方法是最可靠的，但您不需要typeof运算符的括号。看到这个问题。
回答by amit kate
if (variableName){
////implementation
}
this way is more use full than second option
这种方式比第二种选择更充分利用
