JavaScript | date.valueOf() function

The date.valueOf() is an inbuilt function in JavaScript which is used to get the number of milliseconds between 1 January 1970 00:00:00 UTC and the given date.
Syntax:

dateObj.valueOf()

Note: In the above syntax, DateObj is a valid Date object created using Date() constructor whose contents are used to get the number of milliseconds between 1 January 1970 00:00:00 UTC and the given date as the contents of the Date() constructor.

Parameters: This function does not takes any parameter. It is just used along with a Date object created using Date() constructor.

Return Values: It returns the number of milliseconds between 1 January 1970 00:00:00 UTC and the given date as the contents of the Date() constructor.

Below program illustrate the date.valueOf() function:

Output:

845337932000

Errors and Exceptional cases associated with this function.

1. If nothing as a parameter is passed while creating date object but still valueOf() function returns the number of milliseconds between 1 January 1970 00:00:00 UTC and the current date.
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   <script> // Here nothing has been assigned // while creating Date object var dateobj = new Date();    // Getting the number of milliseconds between  //1 January 1970 00:00:00 // UTC and the current date. var B = dateobj.valueOf();    // Printing the calculated number of milliseconds. document.write(B); </script>

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   Output:

   1524387231290

2. Date of a month ranging between 1 to 31. If the date is taken as 35 which is out of the date range, it returns NaN i.e, not a number.
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   <script> // Here a date has been assigned // while creating Date object var dateobj = new Date('October 35, 1996 05:35:32');    // Getting the number of milliseconds between  //1 January 1970 00:00:00 // UTC and the given date. var B = dateobj.valueOf();    // Printing the calculated number of milliseconds. document.write(B); </script>

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   Output:

   NaN

Some Important Points:

• Months, Dates, hours, minutes, seconds, milliseconds should all be in their respective range.Otherwise valueOf() function returns NaN i.e, not a number.
• Range of Months, Dates, hours, minutes, seconds, milliseconds are 0 to 11, 1 to 31, 0 to 23, 0 to 59, 0 to 59, 0 to 999 respectively.

Supported Browsers: The browsers supported by JavaScript date.valueOf() Function are listed below:

• Google Chrome
• Internet Explorer
• Firefox
• Opera
• Safari

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