可能重复:
Javascript === vs == : Does it matter which “equal” operator I use?
When would JavaScript == make more sense than ===?
并且。
为什么在这种情况下我应该选择第二种方法?请告诉我它的优点。
Javascript === vs == : Does it matter which “equal” operator I use?
When would JavaScript == make more sense than ===?
比较字符串与未定义值的下列方法有何区别?
var x;
if(x==undefined)
{
alert(x);
}
并且。
if(x===undefined)
{
alert(x);
}
为什么在这种情况下我应该选择第二种方法?请告诉我它的优点。