Retry until you have a value.

EJS Exercise - Retry.js

function MultiplicatorUnitFailure (message) {
    this.stack = (new Error()).stack;
    this.message = message;
}
MultiplicatorUnitFailure.prototype = Object.create(Error.prototype);
MultiplicatorUnitFailure.prototype.name = 'MultiplicatorUnitFailure';

function primitiveMultiply (a, b) {
	console.log(`a: ${a}; b: ${b}.`);
	let val = a * b;
    if ((Math.floor(val * 100)) % 2 === 0 ) {
        return val;
    } else {
        throw new MultiplicatorUnitFailure('error');
    }
}

function run () {
	var value = null;
    try {
        value = primitiveMultiply(Math.random(), Math.random());
		return value;
    } catch (e) {
		if (e instanceof MultiplicatorUnitFailure) {
			console.log(e);
        } else {
			console.log('error');
        }
    } finally {
        if (value === null) {
            return run();
        } else {
			return value;
        }
    }
}

run();