86 lines
2.6 KiB
JavaScript
86 lines
2.6 KiB
JavaScript
/**
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* Javascript AlphabeticID class
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* (based on a script by Kevin van Zonneveld <kevin@vanzonneveld.net>)
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*
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* Author: Even Simon <even.simon@gmail.com>
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*
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* Description: Translates a numeric identifier into a short string and backwords.
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*
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* Usage:
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* var str = AlphabeticID.encode(9007199254740989); // str = 'fE2XnNGpF'
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* var id = AlphabeticID.decode('fE2XnNGpF'); // id = 9007199254740989;
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**/
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const AlphabeticID = {
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index:'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ',
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/**
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* [@function](https://twitter.com/function) AlphabeticID.encode
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* [@description](https://twitter.com/description) Encode a number into short string
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* [@param](https://twitter.com/param) integer
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* [@return](https://twitter.com/return) string
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**/
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encode:function(_number){
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if('undefined' == typeof _number){
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return null;
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}
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else if('number' != typeof(_number)){
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throw new Error('Wrong parameter type');
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}
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var ret = '';
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for(var i=Math.floor(Math.log(parseInt(_number))/Math.log(AlphabeticID.index.length));i>=0;i--){
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ret = ret + AlphabeticID.index.substr((Math.floor(parseInt(_number) / AlphabeticID.bcpow(AlphabeticID.index.length, i)) % AlphabeticID.index.length),1);
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}
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return reverse(ret);
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},
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/**
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* [@function](https://twitter.com/function) AlphabeticID.decode
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* [@description](https://twitter.com/description) Decode a short string and return number
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* [@param](https://twitter.com/param) string
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* [@return](https://twitter.com/return) integer
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**/
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decode:function(_string){
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if('undefined' == typeof _string){
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return null;
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}
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else if('string' != typeof _string){
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throw new Error('Wrong parameter type');
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}
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var str = reverse(_string);
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var ret = 0;
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for(var i=0;i<=(str.length - 1);i++){
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ret = ret + AlphabeticID.index.indexOf(str.substr(i,1)) * (AlphabeticID.bcpow(AlphabeticID.index.length, (str.length - 1) - i));
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}
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return ret;
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},
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/**
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* [@function](https://twitter.com/function) AlphabeticID.bcpow
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* [@description](https://twitter.com/description) Raise _a to the power _b
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* [@param](https://twitter.com/param) float _a
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* [@param](https://twitter.com/param) integer _b
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* [@return](https://twitter.com/return) string
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**/
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bcpow:function(_a, _b){
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return Math.floor(Math.pow(parseFloat(_a), parseInt(_b)));
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}
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};
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/**
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* [@function](https://twitter.com/function) String.reverse
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* [@description](https://twitter.com/description) Reverse a string
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* [@return](https://twitter.com/return) string
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**/
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function reverse(str){
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return str.split('').reverse().join('');
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};
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export default AlphabeticID
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