What is the correct way to establish an array variable containing objects?

Question

What is the correct way to establish an array variable containing objects?

What is the correct way to declare an object within an array variable? I encountered the following error message:

"TypeError: Cannot set property 'name' of undefined"

Here is the code snippet in question:

let data = []
data[0].name = "john"

javascript

Answer 1

Answer №1

In order to set properties on the first element of an array, you must first declare it as an object.

One method of achieving this is by:

let data = [];
data[0] = {};
data[0].name = "john";

Answer 2

In order to set properties on the first element of an array, you must first declare it as an object.

One method of achieving this is by:

let data = [];
data[0] = {};
data[0].name = "john";

Answer 3

Answer №2

The reason for the error you are encountering is due to the fact that the variable data is an empty array, meaning there are no elements within it at index position 0. Consequently, when attempting to access data[0] (which can be confirmed in the console), you will receive a result of undefined. Trying to assign a new property like name to this undefined value will trigger an error message stating "Cannot set property 'name' of undefined". There are various methods to resolve this issue, one solution being to simply push a new object into the array:

let data = []
data.push({ name : "john"});
console.log(data)

Alternatively, another approach would be to initialize data[0] as an empty object first, allowing you to then assign new properties to it subsequently as follows:

let data = [];
data[0] = {};
console.log(typeof data[0]);  // This will no longer be undefined
data[0].name = "john";
console.log(data)

Answer 4

The reason for the error you are encountering is due to the fact that the variable data is an empty array, meaning there are no elements within it at index position 0. Consequently, when attempting to access data[0] (which can be confirmed in the console), you will receive a result of undefined. Trying to assign a new property like name to this undefined value will trigger an error message stating "Cannot set property 'name' of undefined". There are various methods to resolve this issue, one solution being to simply push a new object into the array:

let data = []
data.push({ name : "john"});
console.log(data)

Alternatively, another approach would be to initialize data[0] as an empty object first, allowing you to then assign new properties to it subsequently as follows:

let data = [];
data[0] = {};
console.log(typeof data[0]);  // This will no longer be undefined
data[0].name = "john";
console.log(data)

Answer 5

Answer №3

It is said that

declare a variable called data which is an empty array and assign the object {"name":"john"} to its first index

Answer 6

It is said that

declare a variable called data which is an empty array and assign the object {"name":"john"} to its first index

What is the correct way to establish an array variable containing objects?

Answer №1

Answer №2

Answer №3

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