wtfjs.js

// Based on : https://github.com/aemkei/jsfuck/blob/master/jsfuck.js
_zero =       +[]     // 0
_false =    !!+[]     // false
_falseStr = !!+[]+[]  // 'false'

_f = (!!+[]+[])[+[]]  // 'f' <= 'false'[0]

_undefined =    [][[]]    // undefined <= [][''] (the property named '' on the array object, which is undefined (property accessors are always cast to strings))
_undefinedStr = [][[]]+[] // 'undefined'

_true =   !+[]  // true <= !0
_one =   +!+[]  // 1 <= +true (true, cast to a number)
_two =   +!+[]+(+!+[])   // 2 <= 1+1
_three = +!+[]+(+!+[])+(+!+[])
_four =  +!+[]+(+!+[])+(+!+[])+(+!+[])
_five =  +!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])

_i = ([][[]]+[])[+!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])]   // 'i' <= 'undefined'[5]
_l = (!!+[]+[])[+!+[]+(+!+[])]                           // 'l' <= 'false'[2]

_fillStr = (!!+[]+[])[+[]]+([][[]]+[])[+!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])]+(!!+[]+[])[+!+[]+(+!+[])]+(!!+[]+[])[+!+[]+(+!+[])]    // 'fill' <= 'f'+'i'+'l'+'l'
_fillFunction = [][(!!+[]+[])[+[]]+([][[]]+[])[+!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])]+(!!+[]+[])[+!+[]+(+!+[])]+(!!+[]+[])[+!+[]+(+!+[])]] // <= []['fill']
_fillFunctionStr = [][(!!+[]+[])[+[]]+([][[]]+[])[+!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])]+(!!+[]+[])[+!+[]+(+!+[])]+(!!+[]+[])[+!+[]+(+!+[])]]+[] // 'function fill() { [native code] }'
_c = ([][(!!+[]+[])[+[]]+([][[]]+[])[+!+[]+(+!+[])+(+!+[])+(+!+[])+(!+[])]+(!!+[]+[])[+!+[]+(+!+[])]+(!!+[]+[])[+!+[]+(+!+[])]]+[])[+!+[]+(+!+[])+(+!+[])] // 'c' <= 'function fill...'[3]