The reason why NaN appears in js

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:

• Try to combine Infinity with another Add or subtract a value
• Try to multiply a number with a string
• Try to convert a number to a boolean

Note:

Not all NaN values ​​are incorrect. In some cases, NaN can be a valid result, for example:

• Math.sqrt(-1) returns NaN, representing the imaginary part of the square root
• parseInt("0x10") Returns NaN, indicating that the conversion of the hexadecimal string to a number failed

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