如何在JavaScript中的forEach循环中调用外部变量

Question

I'm trying to call an external variable in a forEach context. Since I'm using an arrow notation this should make the trick but the variable still comes out as undefined.

This is my code:

transformSlots (slots) {
 var array = slots;
 var newArray;
 array.forEach(element => {
   var newElement = {
     day: dateFns.getDate(element.slot),
     month: dateFns.getMonth(element.slot),
     year: dateFns.getYear(element.slot),
     hour: dateFns.getHours(element.slot),
     numInterview: element.num,
     id_users_pending: 0,
     id_users_accepted: 0
   };
   this.newArray.push(newElement);
 });
 return array;
}

EDIT: If I take .this away the result is exactly the same.

Answer 1

Remove the this . It will make the code look for newarray in the callback and not outside the loop

 transformSlots (slots) { var array = slots; var newArray; array.forEach(element => { var newElement = { day: dateFns.getDate(element.slot), month: dateFns.getMonth(element.slot), year: dateFns.getYear(element.slot), hour: dateFns.getHours(element.slot), numInterview: element.num, id_users_pending: 0, id_users_accepted: 0 }; newArray.push(newElement); }); return array; } 

Answer 2

You should use newArray.push(newElement); instead of this.newArray.push(newElement); .

If you print this in the forEach loop you'll find that the newArray isn't bind to this .