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Jenny Mok
Jenny Mok

Reputation: 2804

lodash isEmpty and has method vs simple check

I can do if(user) { //do something } but I've seen people used lodash to do simple checking. I've read lodash's docs about isEmpty and has methods, but can't figure out why you'd want to use these.

import { isEmpty } from 'lodash'; 

if(isEmpty(user)) { //omg why? }

Upvotes: 15

Views: 32708

Answers (2)

Rajesh
Rajesh

Reputation: 24925

if(user) will pass for empty Object/Array, but they are empty and should be rejected.

Also if(user) will fail for values like 0 or false which are totally valid values.

Using isEmpty() will take care of such values. Also, it makes code more readable.

Point to note is isEmpty(1) will return true as 1 is a primitive value and not a data structure and hence should return true.

This has been stated in Docs:

Checks if value is an empty object, collection, map, or set.

Also as per docs,

Objects are considered empty if they have no own enumerable string keyed properties.

So if you have an object which does not have non-enumerable properties, its considered as empty. In the below example, foo is a part of object o and is accessible using o.foo but since its non-enumerable, its considered as empty as even for..in would ignore it.

var o = Object.create(null);

Object.defineProperty(o, "foo", {
  enumerable: false,
  value: "Hello World"
})
Object.defineProperty(o, "bar", {
  enumerable: false,
  value: "Testing 123"
});


console.log(o)
for (var k in o) {
  console.log(k)
}

console.log(o.foo)

console.log(_.isEmpty(o))
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

Note: This does not mean you should use lodash for such purpose. You can write your own isEmpty function.

Following is something that I use:

This will return true for following cases:

  • {}, [], "", undefined, null, object in above snippet(no enumerable property)
function isEmpty(value){
  return  value === undefined ||
          value === null ||
          (typeof value === "object" && Object.keys(value).length === 0) ||
          (typeof value === "string" && value.trim().length === 0)
}

Upvotes: 39

RajuPedda
RajuPedda

Reputation: 3379

Simple and elegant function for checking the values are empty or not

    function isEmpty(value) {
     const type = typeof value;
     if ((value !== null && type === 'object') || type === 'function') {
       const props = Object.keys(value);
        if (props.length === 0 || props.size === 0) { 
          return true;
        } 
      } 
      return !value;
}

Testing the above method

It will return 'true' for all cases below

console.log(isEmtpy(null)) 
console.log(isEmtpy(0))
console.log(isEmtpy({}))
console.log(isEmtpy(new Set())
console.log(isEmtpy(Object.create(null))
console.log(isEmtpy(''))
console.log(isEmtpy(() => {}))
console.log(isEmtpy(() => [])

Upvotes: 5

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