porting long hex encoding from java to javascript

Question

I want to encode a javascript number-type or string in the same way I encode a Java long.

java

long toEncode = 1397378335821717182L;

String encoded = Long.toHexString(toEncode); //"13647c315b7adebe"

javascript

var toEncode = '1397378335821717182';

var encoded = //missing code, should be'13647c315b7adebe' in the end as well

doing https://stackoverflow.com/a/57805/1052539 I get '13647c315b7adf00'

possible duplicate of [How to convert decimal to hex in JavaScript?](http://stackoverflow.com/questions/57803/how-to-convert-decimal-to-hex-in-javascript) — Quentin, Mar 27 '12 at 12:13
@Quentin not a duplicate, his numbers don't fit in a double so doing it that way he'll lose precision. — wds, Mar 27 '12 at 12:19

score 2 · Answer 1 · edited May 23 '17 at 12:27

2

You'll probably need a javascript bignum library.

~~This one seems to do what you want: http://www-cs-students.stanford.edu/~tjw/jsbn/~~

edit: The one I linked doesn't seem to work. Look around a bit for a nice one (see also https://stackoverflow.com/questions/744099/javascript-bigdecimal-library), but using another google hit, some simple example code is:

<script>
  var toEncode = str2bigInt('1397378335821717182', 10);
  document.write(bigInt2str(toEncode, 16).toLowerCase());
</script>

returns: 13647c315b7adebe

Or with this library (which is, at the very least, better scoped):

<script type="text/javascript" src="biginteger.js"></script>
<script>
  var toEncode = BigInteger.parse('1397378335821717182');
  document.write(toEncode.toString(16).toLowerCase());
</script>

returns: 13647c315b7adebe

edited May 23 '17 at 12:27

Community

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answered Mar 27 '12 at 12:14

wds

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@forste There. I'd recommend the second one. – wds Mar 27 '12 at 12:48
ty again for updating! however, I should have made it more obvious that I need this for node.js. I have put an own answer for this – forste Mar 28 '12 at 13:40
@forste oh yeah didn't see that tag. At least we've got answers for both then. :-) – wds Mar 28 '12 at 15:08

score 1 · Accepted Answer · answered Mar 28 '12 at 13:42

1

For node.js bigdecimal.js works pretty well.

BigDec> (new bigdecimal.BigInteger('1397378335821717182')).toString(16)
'13647c315b7adebe'

answered Mar 28 '12 at 13:42

forste

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porting long hex encoding from java to javascript

2 Answers2