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**How to set up consition that all elements of one arrays must be equal to at least one element of the another array in JavaScript?**without wasting too much if your time.The question is published on by Tutorial Guruji team.

Transforming roman numerals into numbers! A user enter his one roman number, and the code transfers his/her roman number into classic number.

var roman = prompt("Enter roman number", roman); var romandigits = roman.toString().split(""); // spliting roman number entered into an array! let romannumerals = ["M", "D", "C", "L", "X", "V", "I"];

Now condition that suppose to be set is: ALL elements of the array romandigits have to be equal to AT LEAST one element of the array romannumerals!

## Answer

You can create a set of romannumerals

let numeralSet = new Set(romannumerals);

Then you can check that each digit is in that set

let badDigits = romanDigits.filter((c) => !numeralSet.has(c))

and then check whether there are any badDigits:

if (badDigits.length) { console.error(`Invalid roman number ${roman} contains non-digits ${badDigits}`); }

So putting it all together

let roman = prompt("Enter roman number"); let romandigits = [...roman]; let romannumerals = ["M", "D", "C", "L", "X", "V", "I"]; let numeralSet = new Set(romannumerals); let badDigits = romandigits.filter((c) => !numeralSet.has(c)) if (badDigits.length) { console.error(`Invalid roman number ${roman} contains non-digits ${badDigits}`); } else { console.log(`${roman} is OK`); }

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