在javascript中更改for循环以使用forEach

Question

For my project, I have a list of students and am meant to use super basic regular expressions to check their grades. The A and B students are to be added to separate arrays for only those students. The code for doing so is as follows:

const aTest = new RegExp(/(A)/i);
const bTest =  new RegExp(/(B)/i);
const aStudents = [];
const bStudents = [];
for (var i = 0; i < students.length; i++) {
  if (aTest.test(students[i].grade)) {
    aStudents.push(students[i]);
  }
  if (bTest.test(students[i].grade)) {
    bStudents.push(students[i]);
  }
}

However, if I were to use forEach instead of a for loop, how should I go about doing so?

Answer 1

You just need to change every students[i] to the first parameter provided to the forEach (which references the current item being iterated over in the array), probably call it student :

students.forEach(student => {
  if (aTest.test(student.grade)) {
    aStudents.push(student);
  } else if (bTest.test(student.grade)) {
    bStudents.push(student);
  }
});

But if you have a regular expression literal already, there's no need for new RegExp - just assign the regular expression literal to the variable. Also, there's no need for a captured group if you just need to test :

const aTest = /A/i;
const bTest = /B/i;

Or, you might avoid regular expressions entirely and use (ES6) .includes instead:

  if (student.grade.includes('A')) {
    aStudents.push(student);
  } else if (student.grade.includes('B')) {
    bStudents.push(student);
  }

Answer 2

I would use filter instead of forEach , yes it loops over the array twice but the code is clearer to read and understand

const aStudents = students.filter(student => student.grade.match(/A/i));
const bStudents = students.filter(student => student.grade.match(/B/i));