triangle-inequality.js

// a + b > c , a + c > b, b + c > a

function triangleInequality(a, b, c) {
    if (typeof a !== 'number' || typeof b !== 'number' || typeof c !== 'number') {
        return NaN
    }

    return (a + b) > c && (a + c) > b && (b + c) > a;
}

console.log('1', triangleInequality(3, 4, 5));
console.log('2', triangleInequality(1, 2, 4));
console.log('3', triangleInequality('string', 2, 4));