TypeError: Cannot delete property '2' of [object Array] TypeError: Cannot add property 3, object is not extensible errors fixed

Hi friends in this video we are discussing two points 

1.  How to avoid Cannot add property 3, object is not extensible
2.  How to avoid Cannot delete property '2' of [object Array] error
3.  Can we modify/update  an element of sealed array?

When i was working with Object.seal() method,i found that it leads some unexpected error when i used arrays with Object.seal() method in javascript.So i thought that it will helpful for you to understand those errors and How to fix those TypeErrors in the javascript codes

 const sealedArr = [10,20,30];

 Object.seal(sealedArr);

 console.log(Object.isSealed(sealedArr));

 console.log(sealedArr)

Let us examine the above codes line by line 

I declared an array sealedArr 

          const sealedArr = [10,20,30];

I sealed it with Object.seal() method in javascript

          Object.seal(sealedArr);

I print the result  of Object.isSealed() on the terminal and make sure that sealedArr array is sealed with Object.seal() method 

    console.log(Object.isSealed(sealedArr));   //true

I print the entire sealedArr on the terminal using console.log() function 

console.log(sealedArr)  //[ 10, 20, 30 ]

How to avoid Cannot add property 3, object is not extensible

Now i am going to add a new item to  sealedArr array using push method as shown below

const sealedArr = [10,20,30];

Object.seal(sealedArr);

console.log(Object.isSealed(sealedArr));

console.log(sealedArr)

sealedArr.push(40)

when we run the above codes we get the error 

sealedArr.push(40)

          ^

TypeError: Cannot add property 3, object is not extensible

    at Array.push (<anonymous>)

    at Object.<anonymous> (C:\Users\Administrator\Desktop\QuizApp\JS\arrayseal.js:5:11)  

    at Module._compile (node:internal/modules/cjs/loader:1226:14)

    at Module._extensions..js (node:internal/modules/cjs/loader:1280:10)

    at Module.load (node:internal/modules/cjs/loader:1089:32)

    at Module._load (node:internal/modules/cjs/loader:930:12)

    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)

    at node:internal/main/run_main_module:23:47

Node.js v18.14.0

So  We can not  add  items to array sealedArr when sealedArr is sealed with Object.seal() method in javascript

  

How to avoid Cannot delete property '2' of [object Array] error

Now let us  try to remove an item from sealedArr using pop method as shown below 

const sealedArr = [10,20,30];

Object.seal(sealedArr);

console.log(Object.isSealed(sealedArr));

console.log(sealedArr)

sealedArr.pop() 

By executing the above lines of codes we will get the error as shown below 

sealedArr.pop()

          ^

TypeError: Cannot delete property '2' of [object Array]

    at Array.pop (<anonymous>)

    at Object.<anonymous> (C:\Users\Administrator\Desktop\QuizApp\JS\arrayseal.js:5:11)  

    at Module._compile (node:internal/modules/cjs/loader:1226:14)

    at Module._extensions..js (node:internal/modules/cjs/loader:1280:10)

    at Module.load (node:internal/modules/cjs/loader:1089:32)

    at Module._load (node:internal/modules/cjs/loader:930:12)

    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:81:12)

    at node:internal/main/run_main_module:23:47

Node.js v18.14.0

So we understood that We can not  remove  items from array which is sealed with Object.seal() method

Can we modify/update  an element of sealed array?

For example, now i am going to modify element at index 2 of the sealedArr and print the array on the terminal using console.log() method  as shown below 

const sealedArr = [10,20,30];

Object.seal(sealedArr);

console.log(Object.isSealed(sealedArr));

console.log(sealedArr)

sealedArr[2]=300  

console.log(sealedArr)

I got the output on the terminal as shown below

true

[ 10, 20, 30 ] 

[ 10, 20, 300 ]

Yes We can modify alreday existing element in an array which is sealed with Object.seal() method

So by this article we understood what is the reason behind TypeError: Cannot delete property '2' of [object Array]  and  TypeError: Cannot add property 3, object is not extensible.How can we avoid those TypeErrors in our javascript codes