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The reason why NaN appears in JavaScript
NaN (Not-a-Number) is a special value in JavaScript that represents a non-numeric value. It usually appears in the following situations:
1. Trying to convert an invalid string to a number
For example:
<code>const num = parseInt("abc");</code>
The above code tries to convert the character The string "abc" is converted to a number. Since "abc" is not a valid number, the result is NaN.
2. Invalid operations in mathematical operations
For example:
<code>const num = 0 / 0;</code>
The above code attempts to divide by 0, which is an invalid operation, so the result is NaN.
3. Trying to access an uninitialized variable
For example:
<code>let num; console.log(num);</code>
In the above code, the num variable is not initialized, so console.log outputs NaN .
4. Use isNaN() function
isNaN() function is used to test whether a value is NaN. The function returns true if the value is NaN, false otherwise.
5. Other situations
In addition to the above situations, NaN can also appear in the following situations:
Note:
Not all NaN values are incorrect. In some cases, NaN can be a valid result, for example:
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