The usage of tostring() and valueof() and the difference between them

Basically, all JS data types have two methods, valueOf and toString, except null. The two of them solve the problem of javascript value operation and display.

1. The usage is as follows:

toString() method: Returns the string representation of the object.

Object	Operation
Array	Convert the elements of Array is a string. The resulting strings are comma separated and concatenated.
Boolean	If the Boolean value is true, return "true". Otherwise, returns "false".
Date	Returns the text representation of the date.
Error	Returns a string containing the relevant error message.
Function	returns a string in the following format, where functionname is the name of the called toString method function: function functionname( ) { [native code] }
Number	Returns the text representation of the number.
String	returns the value of the String object.
Default	returns "<span style="font-family:NSimsun">[object objectname]</span>", where <span style="font-family:NSimsun">objectname</span> is the name of the object type.

valueOf() method: Returns the original value of the specified object.

Object	Return Value
Array	The elements of the array are converted to strings, these Strings are separated by commas and concatenated together. Its operation is the same as the Array.toString and Array.join methods.
Boolean	Boolean value.
Date	The time stored is the number of milliseconds since midnight on January 1, 1970 UTC.
Function	The function itself.
Number	Number value.
Object	The object itself. This is the default.
String	String value.

2. Common points and differences between the two:

Common points: In JavaScript, the toString() method and The valueOf() method is automatically called when outputting the object.

The difference: when the two coexist, in numerical operations, valueOf is called first, and in string operations, toString is called first.

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