javascript - How to determine if a variable is an empty object, empty array or empty string? - Stack Overflow

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I have an object whose keys can have have values which can be object, string or array.

const obj = {
  key1: 'asdf',
  key2: {},
  key3: ['a','b','c'],
  key4: [],
  key5: '',
}

I have to filter all the keys which are empty i.e empty objects, empty array or empty string.

Is there any other way than writing conditions based on typeof of keys and then checking null ?

I have an object whose keys can have have values which can be object, string or array.

const obj = {
  key1: 'asdf',
  key2: {},
  key3: ['a','b','c'],
  key4: [],
  key5: '',
}

I have to filter all the keys which are empty i.e empty objects, empty array or empty string.

Is there any other way than writing conditions based on typeof of keys and then checking null ?

• javascript
• is-empty

Share Improve this question Follow edited Nov 1, 2021 at 9:15 mmdts 95488 silver badges1717 bronze badges asked Oct 31, 2021 at 12:01 ChandrikaChandrika 14111 gold badge22 silver badges99 bronze badges 0

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4 Answers 4

Sorted by: Reset to default 6

Simply use Object.keys()

if (Object.keys(something).length) console.log("Not empty");

This works for all of strings, arrays, and of course, objects.

You can check the Object.keys documentation for more details, specifically, the examples section and the non-object coercion section, which state:

// simple array const arr = ['a', 'b', 'c'];
console.log(Object.keys(arr)); // console: ['0', '1', '2']

// array-like object const obj = { 0: 'a', 1: 'b', 2: 'c' };
console.log(Object.keys(obj)); // console: ['0', '1', '2']

and

In ES5, if the argument to this method is not an object (a primitive), then it will cause a TypeError.

From ES2015 onwards, a non-object argument will be coerced to an object.

// In ES5 Object.keys('foo');  // TypeError: "foo" is not an object

// In ES2015+ Object.keys('foo');  // ["0", "1", "2"]

For empty strings simple pare the property to "". paring for empty objects and empty arrays can be done using paring the Object.keys of the property length pared to 0.

const obj = {
  key1: 'asdf',
  key2: {},
  key3: ['a','b','c'],
  key4: [],
  key5: '',
}

function filterObject(obj) {
    for (var propName in obj) {
        if (obj[propName] === "" || Object.keys(obj[propName]).length === 0) {
            delete obj[propName];
        }
    }
    return obj;
}

console.log(filterObject(obj));

You can easily achieve the result using Object.keys and reduce

Loop over the keys of object obj using Object.keys and set the properties of new object only if it is not empty

You can check for the type of value using typeof operator

1) string: typeof will return string and check for the length property

2) array: You can use Array.isArray and it will return boolean value whether the object is an array or not

3) object: You can first get all keys using Object.keys and then check if there is any property exist on that object or not using length property

Since, arrays are object in JS, so you can directly use

(typeof value === "object" && Object.keys(value).length)

to check where it is an object and if it contain any property or not

You can create a filter as

if (value !== "" && Object.keys(value).length) acc[key] = value;

const obj = {
  key1: "asdf",
  key2: {},
  key3: ["a", "b", "c"],
  key4: [],
  key5: "",
};

const result = Object.keys(obj).reduce((acc, key) => {
  const value = obj[key];
  if (value !== "" && Object.keys(value).length) acc[key] = value;
  return acc;
}, {});

console.log(result);

const obj = {
  key1: 'asdf',
  key2: {},
  key3: ['a','b','c'],
  key4: [],
  key5: '',
}
Object.keys(obj).map(dt => {if (!obj[dt].length) delete obj[dt]});

console.log(obj)

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