Path: csiph.com!xmission!eternal-september.org!feeder.eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From: Jake Jarvis <pig_in_shoes@yahoo.com>
Newsgroups: comp.lang.javascript
Subject: Re: Array of Files to array of data url
Date: Tue, 19 Jun 2018 12:28:52 +0200
Organization: A noiseless patient Spider
Lines: 31
Message-ID: <pgalt3$hdf$1@dont-email.me>
References: <8dGdnZA1WKvpTbXGnZ2dnUU7-e3NnZ2d@westnet.com.au>
Mime-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Tue, 19 Jun 2018 10:28:51 -0000 (UTC)
Injection-Info: reader02.eternal-september.org; posting-host="832fcc06ea533265a9eed92a23d68efc"; logging-data="17839"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/2/tcPGZyX/ezAZ8NsMTakqDCP9u/VuTY="
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0
Cancel-Lock: sha1:zWOUHrV6sAO94c1DJ0DzH1pkDf4=
In-Reply-To: <8dGdnZA1WKvpTbXGnZ2dnUU7-e3NnZ2d@westnet.com.au>
Xref: csiph.com comp.lang.javascript:35239

Am 19.06.2018 um 11:44 schrieb Andrew Poulos:
> I have this array
> 
> var files = [File, File, null, File];
> 
> and I need to create a new array with the data from each File (or null 
> if it's null).
> 
> I tried
> 
> var newarr = files.map(function(el){
>    if (el === null) return null;
> 
>    var reader = new FileReader();
> 
>    reader.addEventListener("load", function () {
>      return reader.result;
>    }, false);
> 
>    reader.readAsDataURL(el);
> });
> 
> but the array only ever gets populated with null. How can this be done?
> 
> Andrew Poulos

File API is asynchronous. ("Don't call us, we'll call you")

No idea what the big picture is, maybe those new Promise things can help.