Get property value from an object inside of an array

Question

I'm trying to grab class code property value from the object inside each array belonging to "class". (I'm aware my data is convoluted).

This is my student array:

student = [
     {"class":[{
          "code":"PSJ001",
          "professor":"McHale",
          "description":"course description"}]
     },
     {"class":[{
          "code":"ENG303",
          "professor":"Dench",
          "description":"course description"}]
      },
     {"class":[{
          "code":"SCI003",
          "professor":"Biju",
          "description":"course description"}]
     }
]

What I'm trying to get is...

['PSJ001','ENG303','SCI003']

This is what I have...

let classCodes = [];
for (const i in student) {
   classCodes = classCodes.concat(student[i].map(obj => {
       return obj.code;
   }));
}

What am I doing wrong here? (written in jsx)

Your dev console should tell you that students doesn't exist. — zzzzBov
– zzzzBov, Commented Jul 11, 2016 at 18:49

Nenad Vracar · Accepted Answer · 2016-07-11 18:49:38Z

4

You can use map() to get desired result

var student = [{"class":[{"code":"PSJ001","professor":"McHale","description":"course description"}]},{"class":[{"code":"ENG303","professor":"Dench","description":"course description"}]},{"class":[{"code":"SCI003","professor":"Biju","description":"course description"}]}];

var result = student.map(function(e) {
  return e.class[0].code;
});

console.log(result)

answered Jul 11, 2016 at 18:49

Nenad Vracar

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Comments

Lux · Accepted Answer · 2016-07-11 18:52:04Z

0

Basically this will work reliable:

student.map(o => o.class.map(c => c.code)).reduce((obj, arr) => arr.push(...obj) && arr, []);

First we use .map() to get the classes, and inside we use .map() again to get the codes. This gives us a array of arrays. Then we use .reduce() to flatten that array.

answered Jul 11, 2016 at 18:52

Lux

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