The built-in functions on javascript

(1) parseInt () function

　　Syntax: parseInt (string, [n])

 　  This function is mainly the first string of digital to digital conversion, if the string does not start number, the return NaN3;

　　n is used to indicate the data string is a few decimal number, it is not necessary.

　　For example: var str = "123abc"

　　The output is 123

 

(2) parseFloat () function

　　Syntax: parseFloat (string)

　　This function is mainly the first string into a digital floating-point number, if the string does not start number, the return NaN3;

　　For example: var str = "12.12abc"

　　The output is 12.12

 

(3) isNaN () function

　　Syntax: isNaN (num)

　　The main function test whether a value is NaN, Description: num is NaN, the return true, true otherwise

　　For example: var str1 = "12"

　　　　   var str2="12abc"

　　　　The first returns false

　　　　The second returns true 

(4) isFinite () function

　　Syntax: isFinite (num)

　　This function is mainly used to verify whether the parameters which is limited, Note: If num is a limited number of (or may be converted to the limited number), returns true, false otherwise