How can I get hash from string and then string from hash back in javascript

Question

I have a really long (~70,000 characters) string that I want to insert into URL. I need to implement back-forward in a browser, so when the URL changes my app will react and change it's state.

This is the function I use to generate the hash code from the string:

String.prototype.hashCode = function () {
            var hash = 0, i, char;
            if (this.length == 0) return hash;
            var l = this.length;
            for (i = 0; i < l; i++) {
                char = this.charCodeAt(i);
                hash = ((hash << 5) - hash) + char;
                hash |= 0; // Convert to 32bit integer
            }
            return hash;
        };

But how can I get my string back from it's hash?

Edits: Is there any other way to compress such a long URL?

Jim Cote · Accepted Answer · 2013-08-26 12:39:35Z

4

You can't. A hash is a one-way function. 560,000 bits cannot be converted into 32 bits and back again.

answered Aug 26, 2013 at 12:39

Jim Cote

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moritzpflaum · Accepted Answer · 2013-08-26 12:38:28Z

3

With Magic! (Saying it's not possible)

answered Aug 26, 2013 at 12:38

moritzpflaum

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4 Comments

Aleksei Chepovoi Over a year ago

Is there any other way to compress such a long URL?

moritzpflaum Over a year ago

Can you transmit that data via POST? Then, the query string wouldn't be visible.

Aleksei Chepovoi Over a year ago

I don't want to transmit the data. I need to store app state in the url. So when I press back-forward my app will react, also I want to pass url to third party so when they copy-paste it, the app will preserve it's state

moritzpflaum Over a year ago

Well, I guess you could hash the string (containing the full description of the state) and save the related state in a database of some kind. Then, when the hash is passed in the URL, you retrieve the state from the database and build your page with that.

Peter Jaric · Accepted Answer · 2014-02-27 09:45:19Z

0

Depending on your use case, maybe you could have used a URL shortener service to compress your URL. Look at this example: https://twitter.com/peterjaric/status/336941762838945792 (I used tinyurl to compress long data-uris).

Direct link to tinyurl-page: http://tinyurl.com/peterjaric-page1

answered Feb 27, 2014 at 9:45

Peter Jaric

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