Question: How to handle Date object in native C? #4058

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1. rerobika

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   on Jul 27, 2020
2. rerobika commented on Jul 27, 2020

   

   rerobika

   on Jul 27, 2020

   Last edited by rerobika

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   Hello @weixiongmei !

   Unfortunately, currently we do not have any API functions to handle date objects.
   Also the reason is why the the called ecma level functions are not working, it that these methods expect an ecma_number_t instead of a jerry_value_t. If you unpack it into a double variable with jerry_get_number_from_value(args[0]) you can use these internal methods, with the warning of the usage of non-api functions is not the best practice.

   Moreover I can suggest you two better solutions:
   A:

   • ecma_date_year_from_time(args[0]) is almost equivalent to perform Date.prototype.getYear.call(args[0])
   • .call() can be performed with jerry_invoke_function with args[0] as this argument
   • getYear is the property of Date.prototype
   • Date.prototype is the property of Date
   • Date is the property of the global object.
   • So putting the pieces together, use jerry_get_property (global, "Date"), then jerry_get_property(Date, "prototype"), then jerry_get_property(Date.prototype, "getYear") and finally jerry_invoke_function (Date.prototype.getYear, args[0], NULL, 0)

   B:

   • If you have free-time/capacity it'd be great to publish these internal method to the API. I think we should have one single universal function for retrieving information form a date object. So my proposal would look like this:

   typedef enum
   {
     JERRY_DATE_OPERATION_GET_YEAR,
     JERRY_DATE_OPERATION_GET_MONTH,
     // ... and so on
   } jerry_date_operation_t;
   
   jerry_value_t
   jerry_date_get (jerry_date_operation_t operation, jerry_value_t value)
   {
     // step 1: validate date object
     
     // step 2: get the internal date
     ecma_number_t date_num = get_the_stored_internal_date_value() // see ecma_builtin_date_prototype_dispatch_routine
     ecma_number_t result;
     // step 3: choose the operation
     switch (operation) {
       case JERRY_DATE_OPERATION_GET_YEAR: {
         result = ecma_date_year_from_time (date_num);
         break;
       }
       case JERRY_DATE_OPERATION_GET_MONTH: {
         result = ecma_date_month_from_time (date_num);
         break;
       }
   
      // ... and so on
     }
   
     return ecma_make_number_value (result);
   }

   Both options are suitable for resolve your problem, but IMHO the option B would be more future-proof also much efficient as well.
3. weixiongmei commented on Jul 29, 2020

   

   weixiongmei

   on Jul 29, 2020

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   @rerobika Thank you so much~~
4. rerobika

   closed this as completedon Aug 3, 2020