Why I am getting cannot read property byId of undefined

so how can I fix this issue?

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22.09.2020

Adi Автор вопроса

Object.keys(this.props.app.byId)[0] is this wrong?

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22.09.2020

Adi Автор вопроса

any idea what I have done wrong?

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22.09.2020

Adi
any idea what I have done wrong?

which property do you want to read?

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22.09.2020

Adi Автор вопроса

K P
which property do you want to read?

url1

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22.09.2020

Darvesh 🍀
this.props.app?.byId?.url1 ?? default-value

this.props.app?.byId?.url1 ?? default-value

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22.09.2020

Adi Автор вопроса

what is default value

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22.09.2020

Adi
what is default value

Whatever you want. It was just a placeholder

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22.09.2020

Adi Автор вопроса

Darvesh 🍀
Whatever you want. It was just a placeholder

but I don't know the content inside byId it can be url1 or url2 or anything so I just want to extract first key and set it to variable how can I do that case?

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22.09.2020

Adi
what is default value

Important: It will work only on NodeJS version > 14.5

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22.09.2020

Adi Автор вопроса

Darvesh 🍀
Important: It will work only on NodeJS version > 1...

any idea how can I do that?

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22.09.2020

Adi Автор вопроса

let me explain problem url1 and url2 will not be there initially so byId is empty object now once that object is populated I want to set 1st key which is inside byId to a variable

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22.09.2020

Adi
let me explain problem url1 and url2 will not be t...

If it doesn't exist?

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22.09.2020

who even designs such API ? like you are trying to access [0]th property and object keys are interchangeable

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22.09.2020

Object.keys returns array

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22.09.2020

Darvesh 🍀
Important: It will work only on NodeJS version > 1...

For the new features ?

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22.09.2020

Edwing123
For the new features ?

Nullish Coalescing and Optional Chaining

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22.09.2020

Edwing123
Object.keys returns array

No I meant he wanted to access [0] object key order can vary He wouldn't get what he is expecting

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22.09.2020

Darvesh 🍀
Nullish Coalescing and Optional Chaining

Ohh I see

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22.09.2020

Adi Автор вопроса

K P
who even designs such API ? like you are trying...

no idea backend dev's did that I actually solved the problem by doing this: if(this.props.app && this.props.app.byId && Object.keys(this.props.byId).length > 0) { }

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22.09.2020

Adi
no idea backend dev's did that I actually solved t...

Did you miss .app property ?

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22.09.2020

K P · Accepted Answer