Deleting json value with javascript

Question

I have tried to many ways , but i am stuck with a simple function in javascript, and i don't know where i need to looking for ... the problem is this:

I have a Json file like this one:

{
  "blacklist": [
    {
      "email": "[email protected]"
    },
    {
      "email": "[email protected]"
    },
    {
      "email": "[email protected]"
    },
    {
      "email": "[email protected]"
    },
    {
      "email": "[email protected]"
    }
  ]
}

I would like simple remove an email with a simple function like this one:

 function cancel(email) // parameter that contain the value to delete
{
  let rawdata = fs.readFileSync('pvt.json'); //get local json file
  let mydata = JSON.parse(rawdata); //parsing rawdata 

  var key = email; //setting up key
  delete mydata.blacklist[key]; //using delete function for delete an element

  let data = JSON.stringify(mydata, null, 2); //stringify the result
  fs.writeFileSync('pvt.json', data); // overwrite local file with new one with all changes
}

the problem is ... it doesn't works ... i don't know why ... i tried to read the documentation, but i didn't found any solution 😢

What's the value of your email variable? It appears out of nowhere in the code. Is it a string containing the email address you want to remove? — T.J. Crowder
– T.J. Crowder, Commented May 2, 2020 at 14:39
@T.J. Thank you for the reply! Yes, email is a string var that contain the email to delete. Sorry, i will istant update the code ! — Zenek
– Zenek, Commented May 2, 2020 at 14:41
@ChandraShekhar key is the vaule to delete, email is the parameter passed in the function that contain the value to delete — Zenek
– Zenek, Commented May 2, 2020 at 14:42

T.J. Crowder · Accepted Answer · 2020-05-02 14:51:38Z

1

The delete operator is for removing a property from an object, using the property's name. You're trying to remove an entry from an array, using the value of a property of an object in the array.

Assuming email is a variable containing the email address in the entry you want to remove, filter is one easy way to do that:

mydata.blacklist = mydata.blacklist.filter(entry => entry.email !== email);

filter builds a new array from the entries in the original array that meet the criteria in the callback — in this case, that their email property doesn't match the email address you want to remove.

If you wanted to modify the array in place rather than creating a new one, you'd use findIndex and splice:

const index = mydata.blacklist.findIndex(entry => entry.email === email);
if (index !== -1) {
    mydata.blacklist.splice(index, 1); // Remove the entry at the index
}

edited May 2, 2020 at 14:51

answered May 2, 2020 at 14:39

T.J. Crowder

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7 Comments

Zenek Over a year ago

Thank you for the reply! yes, email is the value passed as parameter that we need to remove ... and yes, i already used filter, but i don't understand how to delete the value after filtered

T.J. Crowder Over a year ago

@Zenek - You don't have to delete it after you've filtered it out. Filtering it out is, effectively, deleting it.

Zenek Over a year ago

TypeError: mydata.findIndex is not a function

T.J. Crowder Over a year ago

@Zenek - Sorry, should have been mydata.blacklist.

Zenek Over a year ago

Thank you for the reply. I tried to use your function, but if i can, i would like understand what did you used (i don't like copy/paste). Thank to your function we will obtain a new array called "mydata.blacklist" that doesn't have the email searched in ?

|

xdeepakv · Accepted Answer · 2020-05-02 14:47:58Z

0

Delete works to delete a key-value from an object. Here you have an array of items[objects]. You should use filter to remove unwanted element.

Update:

function cancel(selectedEmail) {
  let rawdata = fs.readFileSync("pvt.json"); //get local json file
  let mydata = JSON.parse(rawdata); //parsing rawdata
  mydata.blacklist = mydata.blacklist.filter(
    (item) => item.email !== selectedEmail.email
  );
  fs.writeFileSync("pvt.json", JSON.stringify(mydata, null, 2)); // overwrite local file with new one with all changes
}

Sample:

const info = {
  blacklist: [
    {
      email: "[email protected]",
    },
    {
      email: "[email protected]",
    },
    {
      email: "[email protected]",
    },
    {
      email: "[email protected]",
    },
    {
      email: "[email protected]",
    },
  ],
};
const selectedEmail = {email: "[email protected]"}

info.blacklist = info.blacklist.filter(item => item.email !== selectedEmail.email)
console.log(info)

edited May 2, 2020 at 14:47

answered May 2, 2020 at 14:41

xdeepakv

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4 Comments

Zenek Over a year ago

Thank you for the reply. I tried this one , but it doesn't works. Email rest in the array and in the json file :/

xdeepakv Over a year ago

can u see what is coming in log..email. If it is not object.. then use info.blacklist.filter(item => item.email !== email)

Zenek Over a year ago

probably is my fault... just let me understand what you did : i have added the function code that you wrote in my js server-side script. Then you have wrote a "sample" of your code, but it doesn't have the cancel function linked in to (?) so... (?)

xdeepakv Over a year ago

sample is for u to run and see output working. kind of logic to understand. U write ur own server code.

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