CODEWITHSUNDEEP
javascriptarraysjsontypescript
André Monteiro
André Monteiro

Reputation: 78

Is there a mixed data structure between array and JSON?

A team handed out their project to mine, in which I saw something strange. They first declared a variable as an array:

private myvariable: Array<any> = [];

But then in the code, they were using it as an object, doing things like: 

myvariable['key'] = { 'prop': 'val' }

This ends up evaluated as something strange: 

[key: {...}]

Does someone know how to explain this data structure?

Upvotes: 0

Views: 53

Answers (1)

Carsten Massmann
Carsten Massmann

Reputation: 28226

An Array is basically a JavaScript Object and can have properties and methods associated with it, just like a "pure" object. It being an Array will affect its behaviour when it comes to methods like .toString() or when it is being converted by JSON.stringify(). Its properties will not be found in the JSON representation.

You can visualise it's properties by casting (Object.assign()-ing) it to an object like in:

var array=[1,2,3];
array.key='hello';
console.log(JSON.stringify(Object.assign({},array)));
// {"0":1,"1":2,"2":3,"key":"hello"}

This will show the array as an object (the index numbers will appear like string property names with their associated values).

Upvotes: 3

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