Question

164

how to convert this nested object into a flat object?

rated 0 times [ 170] [ 6] / answers: 1 / hits: 54156 / 9 Years ago, tue, december 29, 2015, 12:00:00

Sorry I don't know how to phrase the question title. Please help edit if possible.

I have an object like this:

{

    a: 'jack',

    b: {

        c: 'sparrow',

        d: {

           e: 'hahaha'

        }

    }

}

I want to make it look like:

{

    'a': 'jack',

    'b.c': 'sparrow',

    'b.d.e': 'hahaha'

}



// so that I can use it this way:

a['b.d.e']

jQuery is ok too. I know for the nested object, I can use a.b.d.e to get hahaha, but today I have to use it like a['b.d.e'] -_-!!!
How can I achieve this? Thanks in advance :)

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daren

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3 Years ago

answered 9 Years ago jazminkyrap · Accepted Answer

You could use a recursive function to crawl the object and flatten it for you.

var test = {

    a: 'jack',

    b: {

        c: 'sparrow',

        d: {

            e: 'hahaha'

        }

    }

};



function traverseAndFlatten(currentNode, target, flattenedKey) {

    for (var key in currentNode) {

        if (currentNode.hasOwnProperty(key)) {

            var newKey;

            if (flattenedKey === undefined) {

                newKey = key;

            } else {

                newKey = flattenedKey + '.' + key;

            }



            var value = currentNode[key];

            if (typeof value === object) {

                traverseAndFlatten(value, target, newKey);

            } else {

                target[newKey] = value;

            }

        }

    }

}



function flatten(obj) {

    var flattenedObject = {};

    traverseAndFlatten(obj, flattenedObject);

    return flattenedObject;

}



var flattened = JSON.stringify(flatten(test));

console.log(flattened);

One way to reverse this, if needed, is a nested set of loops. There is probably a cleaner way to accomplish this though:

var test = {'a':'jack','b.c':'sparrow','b.d.e':'hahaha'};



function expand(target, keySeparator) {

    var result = {};

    for (var key in target) {

        if (target.hasOwnProperty(key)) {

          var nestedKeys = key.split(keySeparator);

          // Get the last subKey

          var leaf = nestedKeys[nestedKeys.length - 1];

          // Get all subKeys except for the last

          var branch = nestedKeys.slice(0, nestedKeys.length - 1);

          

          var currentTarget = result;

          for (var i = 0; i < branch.length; i += 1) {

            var subKey = nestedKeys[i];

            // If this is the first time visiting this branch, we need to instantiate it

            if (currentTarget[subKey] === undefined) {

              currentTarget[subKey] = {};

            }

            // Visit the branch

            currentTarget = currentTarget[subKey];

          }

          currentTarget[leaf] = target[key];

        }

    }

    return result;

}



var expanded = JSON.stringify(expand(test, .));

console.log(expanded);