#escape64

Intro

Using standard Base64 in URLs requires encoding of +, / and = characters into special percent-encoded hexadecimal sequences (+ becomes %2B, / becomes %2F and = becomes %3D), which makes the string unnecessarily longer.
For this reason, modified Base64 for URL variants exist, where the + and / characters of standard Base64 are respectively replaced by - and _, so that using URL encoders/decoders are no longer necessary and have no impact on the length of the encoded value

Both above solutions lack a very usefull property for URLs. Double Click mouse selection!

Definition

Escape64 is a variable length variant of Base64 that solves this in a intiutive way.
_ is used as an escape character and we define the following escape sequences

    __      beginging of an Escape64 sequence (optional)
    
    _p      encodes a (+) of Base64
    _d      encodes a (/) of Base64
    _q      encodes a (=) pad character of Base64
    
    _b      marks breaks inside an Escape64 sequence (optional)
    
    _*      Reserved. Where (*) can be any char not expicitly mentioned above.   

Example Implementation

var x = 'asdf+ff/f+ff/dd+ddAd==';                                         //base64 value
var y = x.replace(/[+]/g,'_p').replace(/[\/]/g,'_d').replace(/[=]/g,'_q');//escape64 value encode
var z = y.replace(/_p/g,'+').replace(/_d/g,'/').replace(/_q/g,'=');       //escape64 value decode

console.log(x, y, z);
console.log(z);
console.log(x==z);

Links

https://en.wikipedia.org/wiki/Base64