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javascriptis-empty

How to determine if a variable is an empty object, empty array or empty string?

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 ?

Solution

  • 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"]