Printer Errors
In a factory a printer prints labels for boxes. For one kind of boxes the printer has to use colors which, for the sake of simplicity, are named with letters from a to m.
The colors used by the printer are recorded in a control string. For example a “good” control string would be aaabbbbhaijjjm meaning that the printer used three times color a, four times color b, one time color h then one time color a…
Sometimes there are problems: lack of colors, technical malfunction and a “bad” control string is produced e.g. aaaxbbbbyyhwawiwjjjwwm with letters not from a to m.
You have to write a function printer_error which given a string will output the error rate of the printer as a string representing a rational whose numerator is the number of errors and the denominator the length of the control string. Don’t reduce this fraction to a simpler expression.
The string has a length greater or equal to one and contains only letters from ato z.
Examples:
s="aaabbbbhaijjjm"
error_printer(s) => "0/14"
s="aaaxbbbbyyhwawiwjjjwwm"
error_printer(s) => "8/22"
reply
function printerError(s) {
let vaild = 'abcdefghijklm';
return `${s.split('').reduce((s,x)=>{
return s += vaild.includes(x)?0:1
},0)}/${s.length}`
}
