I'm trying to get the total length count of each array within their respective objects...

campus : {
    "mchale": {
        "classes":["ESJ030", "SCI339"], // get the length
        "faculty":["Hardy", "Vikrum"]   // get the length
     },
    "lawerence":{
        "classes":["ENG001"],  // get the length
        "faculty":["Speedman", "Lee", "Lazenhower"] // get the length
     }
}

This is what I have:

const arrCount = campus.mchale.classes.length + campus.mchale.faculty.length + campus.lawerence.classes.length ...

Is there a better/prettier way to go about this to retrieve the total count of each array present in the objects?

I'm trying to get the total length count of each array within their respective objects...

campus : {
    "mchale": {
        "classes":["ESJ030", "SCI339"], // get the length
        "faculty":["Hardy", "Vikrum"]   // get the length
     },
    "lawerence":{
        "classes":["ENG001"],  // get the length
        "faculty":["Speedman", "Lee", "Lazenhower"] // get the length
     }
}

This is what I have:

const arrCount = campus.mchale.classes.length + campus.mchale.faculty.length + campus.lawerence.classes.length ...

Is there a better/prettier way to go about this to retrieve the total count of each array present in the objects?

• javascript
• arrays

Share Follow asked May 20, 2016 at 14:47 ModelesqModelesq 5,4222020 gold badges6363 silver badges8989 bronze badges 0

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3 Answers 3

Sorted by: Reset to default 3

You can use Object.keys with map and reduce to collect the arrays, get their length, then sum those values:

const data = {
    "mchale": {
        "classes":["ESJ030", "SCI339"], // get the length
        "faculty":["Hardy", "Vikrum"]   // get the length
     },
    "lawerence":{
        "classes":["ENG001"],  // get the length
        "faculty":["Speedman", "Lee", "Lazenhower"] // get the length
     }
};

const count = Object.keys(data).map(campusName => {
  const campus = data[campusName];
  return Object.keys(campus).map(key => campus[key].length).reduce((p, c) => p + c, 0);
}).reduce((p, c) => p + c, 0);
console.log(count);

You can use Array#reduce with Object.keys() as follow.

Object.keys(campus).reduce((a, b) => campus[b].classes.length +
    campus[b].faculty.length + a, 0);

var campus = {
    "mchale": {
        "classes": ["ESJ030", "SCI339"], // get the length
        "faculty": ["Hardy", "Vikrum"] // get the length
    },
    "lawerence": {
        "classes": ["ENG001"], // get the length
        "faculty": ["Speedman", "Lee", "Lazenhower"] // get the length
    }
};

var length = Object.keys(campus).reduce((a, b) => campus[b].classes.length + campus[b].faculty.length + a, 0);
console.log(length);

You can recursively traverse object key's and sum all lengths of array objects:

var campus = {
    "mchale": {
        "classes":["ESJ030", "SCI339"],
        "faculty":["Hardy", "Vikrum"]
     },
    "lawerence":{
        "classes":["ENG001"],
        "faculty":["Speedman", "Lee", "Lazenhower"]
     }
};

function totalArrayLength(obj) {
    return Object.keys(obj).reduce((total, key) => {
        if (Array.isArray(obj[key])) {
            total += obj[key].length;
        } else if (typeof obj[key] === 'object') {
            total += totalArrayLength(obj[key]);
        }
        return total;
    }, 0);
}

console.log(totalArrayLength(campus));