Remove null values from json file javascript

Question

I am new to javascript and I have encountered a problem I need to remove all null values from a json file. But I have not been able to get it I have tried different methods that I found on the site but they do not work for me. One of the ways I found below. I just have a problem as I said before the json file I get it with JSON.stringify and by using the code that removes null I get this "{\" name \ ": \" Ann \ " , \ "children \": [null, {\ "name \": \ "Beta \", \ "children \": [null, null, null]}, null]} ".

function Parent(name){
    this.name = name;
    this.children=new Array(null,null,null);
}

Parent.prototype.getName = function(){
return this.name;
};

Parent.prototype.setName = function(name) { 
 this.name=name; 
};

Parent.prototype.getChildren = function(){
 return this.children;
};

Parent.prototype.setChildren = function(parent) { 
 this.children=parent; 
};

var parent = create(aux,new Parent(""));// This method create tree parent
var o = parent;
j = JSON.stringify(o, (k, v) => Array.isArray(v) 
       && !(v = v.filter(e => e !== null && e !== void 0)).length ? void 0 : v, 2 )
     alert (j);

Json file:

{
  "name": "Ann",
  "children":
  [
    null,
    {
      "name": "Beta",
      "children":
      [
        null,
        null,
        null
      ]
    },
    null
  ]
}

What I expect:

{
  "name": "Ann",
  "children":
  [
    {
      "name": "Beta"
    }
  ]
}

Because I don't think you want to delete object properties. It looks like you need to splice out null elements of arrays instead. — Andy
– Andy, Commented Dec 2, 2017 at 22:25
Are you sure you want to modify the original object? I'd consider creating a new filtered object instead of updating and deleting properties from the original reference — Matias Cicero
– Matias Cicero, Commented Dec 2, 2017 at 22:30
@MatiasCicero Relax, it's from a JSON file, so once it is parsed, it's already a copy. — blex
– blex, Commented Dec 2, 2017 at 22:33
@blex From the point of view of the method, this can be any object. I'm just saying so the caller of the method does not get any unexpected behavior. Immutability over mutability, if possible. — Matias Cicero
– Matias Cicero, Commented Dec 2, 2017 at 22:36

Slai · Accepted Answer · 2017-12-02 23:29:32Z

7

JSON.parse and JSON.stringify accept replacer function to modify the values:

j = '{ "name": "Ann", "children": [ null, { "name": "Beta", "children": [ null, null, null ] }, null ] }'

o = JSON.parse(j, (k, v) => Array.isArray(v) ? v.filter(e => e !== null) : v )

console.log( o )

o = { "name": "Ann", "children": [ null, { "name": "Beta", "children": [ null, null, null ] }, null ] }

j = JSON.stringify(o, (k, v) => Array.isArray(v) ? v.filter(e => e !== null) : v, 2 )

console.log( j )

To remove the empty array too:

o = { "name": "Ann", "children": [ null, { "name": "Beta", "children": [ null, null, null ] }, null ] }

j = JSON.stringify(o, (k, v) => Array.isArray(v) 
                                && !(v = v.filter(e => e)).length ? void 0 : v, 2 )

console.log( j )

edited Dec 2, 2017 at 23:29

answered Dec 2, 2017 at 22:56

Slai

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4 Comments

pete Over a year ago

Your solution is fantastic I just have a problem as I said before the json file I get it with JSON.stringify and by using the code that removes the empty array too: I get this "{\" name \ ": \" Ann \ " , \ "children \": [null, {\ "name \": \ "Beta \", \ "children \": [null, null, null]}, null]} ". What am I doing wrong?

Slai Over a year ago

@pete maybe the values are not null, but undefined or missing. Try the update.

pete Over a year ago

Keep going the same thing is very strange. With the json burned it works. But getting it with JSON.stringify does not work. JavaScript only seeks to annoy me.

Slai Over a year ago

@pete if the updated version doesn't work either, can you update your question with the code that reproduces the issue, or make a separate question with a MVCE

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