Get a specific item length in array object [nodejs]

Question

I want to get the length of an array that match the value specified by the condition.

var school = {
    student : {
        name: Json,
        class: 0,
        type: male,
        average: B+
    },
    student : {
        name: Afrado,
        class: 0,
        type: male,
        average: C+
    },
    student : {
        name: Emily,
        class: 1,
        type: female,
        average: A+
    }
};

I'd like to know the lengh of class "0" but I don't know how to resolve this case?
In this case I can get the length of "2" for my results.

Have a nice day~ :)

Ramesh Thiruchelvam · Accepted Answer · 2019-12-05 05:43:21Z

2

Your array is not structured properly, what you need to do is to filter and get the length of the filtered items.

var school = [
  {
    name: "Json",
    class: 0,
    type: "male",
    average: "B+"
  },
  {
    name: "Afrado",
    class: 0,
    type: "male",
    average: "C+"
  },
  {
    name: "Emily",
    class: "1",
    type: "female",
    average: "A+"
  }
];

console.log(school.filter(student => student.class === 0).length);

answered Dec 5, 2019 at 5:43

Ramesh Thiruchelvam

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Comments

Siddharth Nayar · Accepted Answer · 2019-12-05 05:54:36Z

0

You can use the reduce function to avoid creating a temporary array with filter.

console.log(school.reduce((count, student) => student.class === 0 ? ++count : count, 0));

answered Dec 5, 2019 at 5:54

Siddharth Nayar

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Comments

mohammad javad ahmadi · Accepted Answer · 2019-12-05 06:08:15Z

you can also use this way:

var school = [
  {
    name: "Json",
    class: 0,
    type: "male",
    average: "B+"
  },
  {
    name: "Afrado",
    class: 0,
    type: "male",
    average: "C+"
  },
  {
    name: "Emily",
    class: "1",
    type: "female",
    average: "A+"
  }
];

function search(className, myArray){
    var countClass = 0;
    for (var i=0; i < myArray.length; i++) {
        if (myArray[i].class === className) {
            countClass++;
        }
    }
    return countClass;
}

function searchForeach(className, myArray){
    var countClass = 0;
    myArray.forEach((item) => {
      if (item.class === className) {
        countClass++;
      }
    });
    return countClass;
}

function searchFind(className, myArray){
    var countClass = 0;
    myArray.find((item, index) => {
      if (item.class === className) {
        countClass++;
      }
    });
    return countClass;
}




console.log(search(0, school));
console.log(searchForeach("1", school));
console.log(searchFind(0, school));

second way use find:

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