Math，Number

①Math.trunc()

Math.trunc() method is used to remove the decimal part of a number and return the integer part.

When the parameter is a non-numeric value, the Math.trunc() method will first use Number() to convert it into a numerical value. If the integer part of the value cannot be obtained, such as a string or NaN or a null value, it will return NaN.

②Math.sign()

Math.sign() method is used to determine whether a number is positive, negative or 0
(1) If the parameter is a positive number, +1
is returned (2) If the parameter is a negative number, -1
is returned (3) If the parameter is 0, return 0
(4) The parameter is -0 and returns -0
(5) Other values ​​return NaN

③Math.cbrt()

Math.cbrt() method is used to calculate the cube root of a number

If the parameter is not a numerical value, Math.cbrt() also first uses the Number() method to convert it into a numerical value.
Conversion failure returns NaN.

Number.isNaN() is used to check whether a value is NaN.

Number.isNaN(NaN) // true
Number.isNaN(15) // false
Number.isNaN('15') // false
Number.isNaN(true) // false
Number.isNaN(9/NaN) // true
Number.isNaN('true'/0) // true
Number.isNaN('true'/'true') // true

Number.isInteger() is used to determine whether a value is an integer.

Number.isInteger(25) // true
Number.isInteger(25.0) // true
Number.isInteger(25.1) // false
Number.isInteger("15") // false
Number.isInteger(true) // false

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