How to combine to arrays?

Question

I got item a, which is an javascript object I think?

const item = myItem.getAsFile();

which returns something like

lastModified: 1521979332955
name: "image.png"
size: 15254
type: "image/png"
webkitRelativePath: ""

Next I create a object url:

const preview = window.URL.createObjectURL(item);

which returns "blob:https://localhost:3000/..."

Now I want to "push" preview: "blob:https://localhost:3000/..." inside my const item, so that next to lastModified, name, size, etc. preview: will be listed.

How can I do this?

Change `const` to `var` or `let` so you can change item. Then use `item.preview = preview` to add the attribute to the object. — Tostifrosti, Mar 25 '18 at 12:11
@Tostifrosti `const` [does not prevent](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const#Description) the modification of `item`. It just disables storing another value in `item`. — axiac, Mar 25 '18 at 12:13
It is really simple thing, seems it must not be a question. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects — Vayrex, Mar 25 '18 at 12:13
@axiac Oh my bad! You apparently need to use Object.freeze() to make the object completely immutable. — Tostifrosti, Mar 25 '18 at 12:18
Possible duplicate of [Add a property to a JavaScript object using a variable as the name?](https://stackoverflow.com/questions/695050/add-a-property-to-a-javascript-object-using-a-variable-as-the-name) — FisNaN, Mar 25 '18 at 12:28

score 2 · Accepted Answer · edited Mar 25 '18 at 17:09

2

You can do the following:

item.preview = preview;

if you don't want to change the origin item, you can use Object.assign

let newItem = Object.assign({}, item, {preview: preview})

edited Mar 25 '18 at 17:09

Marian Rick

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answered Mar 25 '18 at 12:12

欧阳维杰

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How to combine to arrays?

1 Answers1