CODEWITHSUNDEEP
javascriptjsonrecursion
Michal Olechowski
Michal Olechowski

Reputation: 646

Java Script: loop through JSON

How would you loop through provided JSON to get every grade from all the years and paste them in array?I'm quite new to JS so any explanation is welcome. Expected array for this example would be [2,4,2,5,4,5,4.5,2,3.5,5,5,5,5,5]

{
    "first_name": "Ala",
    "last_name": "Kowalski",
    "birth_date": "29 AUG 1990",
    "indeks_number": "9454530",
    "year_of_study": "2",
    "courses": {
        "2013": {
            "AlgorithmsI": {
                "grades": {
                    "exercices": [
                        2,
                        4
                    ],
                    "lecture": [
                        2,
                        5
                    ]
                }
            },
            "BasicPhysicsI": {
                "grades": {
                    "exercices": [
                        4
                    ],
                    "lecture": [
                        5
                    ]
                }
            },
            "ProgrammingI": {
                "grades": {
                    "exercices": [
                        4.5
                    ],
                    "lecture": [
                        2,
                        3.5
                    ]
                }
            }
        },
        "2014": {
            "ProgrammingII": {
                "grades": {
                    "exercices": [
                        5
                    ],
                    "lecture": [
                        5
                    ]
                }
            },
            "BasicPhysicsII": {
                "grades": {
                    "exercices": [
                        5
                    ],
                    "lecture": [
                        5
                    ]
                }
            },
            "AlgorithmsII": {
                "grades": {
                    "exercices": [
                        5
                    ],
                    "lecture": [
                        5
                    ]
                }
            }
        }
    }
}

Upvotes: 0

Views: 929

Answers (4)

Jackson Ray Hamilton
Jackson Ray Hamilton

Reputation: 9466

Recursive:

function each(object, iterator) {
    Object.keys(object).forEach(function (key) {
        var value = object[key];
        iterator(value, key);
    });
}

function inArray(array, value) {
    return array.indexOf(value) > -1;
}

function isPlainObject(value) {
    return !!value && typeof value === 'object' && value.constructor === Object;
}

function getGrades(data) {
    var grades = [];
    each(data, function (value, key) {
        if (inArray(['exercices', 'lecture'], key)) {
            grades = grades.concat(value);
        } else if (isPlainObject(value)) {
            grades = grades.concat(getGrades(value));
        }
    });
    return grades;
}

You can test this in Node.js with:

var assert = require('assert');
assert.deepEqual(getGrades(fixture),
                 [2, 4, 2, 5, 4, 5, 4.5, 2, 3.5, 5, 5, 5, 5, 5, 5]);

Where fixture is your JSON.

Upvotes: 0

Beartums
Beartums

Reputation: 1350

var grades = [];
var obj = <your Object>;

processObj(obj);

function processObj(obj) {
    for (var n in obj) {
        if (n=='exercices' || n=='lectures') {
            for (var j=0;j<obj[n].length;j++) {
                grades.push(obj[n][j]);
            }
        } else {
            processObj(obj[n]);
        }
     }
}

Upvotes: 0

user663031
user663031

Reputation:

I might use JSON.stringify as a way to iterate through the object:

grades = [];
JSON.stringify(obj, function(key, value) {
    if (key === 'grades') 
        grades = grades.concat(value.exercices, value.lecture);
    return value;
});

How this works

JSON.stringify is designed to convert an object into a JSON string. To do that, it iterates over all values in the object at all levels. It also provides the ability to specify a replacer parameter, which is a function called with each key/value pair it encounters. Here, we use the replacer not to control the stringification, but to get a chance to examine each key/value pair to see if the key is 'grades', and if so add those grades to the grades array. We have to return value so that JSON.stringify keeps iterating. The actual result from JSON.stringify is irrelevant and thrown away.

Upvotes: 2

caslaner
caslaner

Reputation: 413

Hi you can try this one.

function looop(jsonob) {
    var gradeArray = [];
    for (years in jsonob.courses) {
        for (lessons in jsonob.courses[years]) {
            for (x in jsonob.courses[years][lessons].grades.exercices) {
                gradeArray.push(jsonob.courses[years][lessons].grades.exercices[x]);
            }
            for (x in jsonob.courses[years][lessons].grades.lecture) {
                gradeArray.push(jsonob.courses[years][lessons].grades.lecture[x]);
            }
        }
    }
    return gradeArray;
}

Upvotes: 0

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