Comparing empty list from JSON to an empty list

Question

I am trying to check in JavaScript if a value from a json is an empty list or not. I tried obviously json.bundleProductSummaries != []. This doesn't work, however this works:

JSON.stringify(json.bundleProductSummaries) != JSON.stringify([])

My json :

  {
    "bundleProductSummaries": [

    ]
  }

My code :

fs = require('fs')
body = fs.readFileSync('./json.txt',{encoding : 'utf-8'})
// ---- Parsing de body ----
let json = JSON.parse(body);
let colored = null;

if(json.bundleProductSummaries != []){
    json = json.bundleProductSummaries[0];
}

Thank you for your future answers ! Syndorik

Answer 1

You need to check length

json.bundleProductSummaries.length === 0

Because in JS

 console.log([] === [] ) 

as they are two different memory reference.

But when two array will evaluate to true ?

When they both the value you're comparing is having same reference

 let a = [] console.log(a === a) 

Answer 2

You can check the length of the Array to check if its empty

 let obj = { "bundleProductSummaries": [] } console.log(obj.bundleProductSummaries.length === 0) 

In you case you can just don't need to compare because you are using it in if statement and 0 is itself a falsy value.

 let obj = { "bundleProductSummaries": [] } if(!obj.bundleProductSummaries.length){ console.log("Array is empty") }