IE11 and JavaScript array.map()

Question

I have run into problem under IE11. It throws an error

Expected: ":"

for that line of code:

this.aAttachments = MessageStore.message().attachments().map(({fileName,mimeType,fileType,fileNameExt,download}) => [fileName,mimeType,fileType,fileNameExt,download]);

in the part

{fileName,mimeType,fileType,fileNameExt,download}

instead of commas.

Documentation says that IE support fully map since IE9

Any clue on that?

The question is, does MessageStore.message().attachments() return an Array or an "array-like" object? In IE, you can only call .map() on true arrays, not "array-like" objects. If the return value is an array-like object, you'll need to explicitly convert it to an Array with Array.prototype.slice.call(MessageStore.message().attachments()). — Scott Marcus
– Scott Marcus, Commented Jun 13, 2018 at 21:20
Imho the destructuring is more a problem. IE has no support for even basic destructuring. Btw the error message already hints at that, it expects a : for a key:value pair because it's the only thing the parser could possibly expect. — ASDFGerte
– ASDFGerte, Commented Jun 13, 2018 at 21:20
@ScottMarcus it returns an array of objects like [{key:value, key1:value},{key:value, key1:value},...] — JackTheKnife
– JackTheKnife, Commented Jun 13, 2018 at 21:22
As a currently deleted (for different reasons) answer stated: IE doesnt even support arrow functions. Poor souls who have to support IE11 or even lower, really. I hope i never ever have to. — ASDFGerte
– ASDFGerte, Commented Jun 13, 2018 at 21:37

obermillerk · Accepted Answer · 2018-06-13 22:03:25Z

4

I don't think the issue is with map, I think the issue is that you're using a shortcut for assigning object properties to their own variables in that part you specified. I believe this is a relatively new feature to javascript so likely not supported by IE since it seems to lag far behind. I would suggest changing your inline function to

(obj) => [obj.fileName,obj.mimeType,obj.fileType,obj.fileNameExt,obj.download]

and see if that fixes it.

EDIT: Some people are also saying that IE does not support arrow functions either, so make that

function(obj) { return [obj.fileName,obj.mimeType,obj.fileType,obj.fileNameExt,obj.download]; }

edited Jun 13, 2018 at 22:03

answered Jun 13, 2018 at 21:25

obermillerk

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2 Comments

Barmar Over a year ago

IE doesn't support arrow functions, either, you need function(obj)

JackTheKnife Over a year ago

Looks promising when running on standalone IE11. I will verify how it comes when IE11 is emended in the main application.

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