Specific example of js judging whether the input is a number_javascript skills

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Note Ming: In JavaScript, to determine whether the content entered by the user is a number, we only need to use isNaN to determine it.
isNaN(numValue) The required numvalue parameter is the value to be checked whether it is NAN
If the value is NaN, then the isNaN function returns true, otherwise it returns false
The typical case of using this function is to check parseInt and The return value of the parseFloat method. Alternatively, a variable can be compared with itself. If the result of the comparison is not equal, then it is NaN . This is because NaN is the only value that is not equal to itself.