lib/rules/new-cap.js
function checkArray(obj, key, fallback) {

    /* istanbul ignore if */
    if (Object.prototype.hasOwnProperty.call(obj, key) && !Array.isArray(obj[key])) {
        throw new TypeError(`${key}, if provided, must be an Array`);
    }
    return obj[key] || fallback;
}
function checkArray(obj, key, fallback) {

    /* istanbul ignore if */
    if (Object.prototype.hasOwnProperty.call(obj, key) && !Array.isArray(obj[key])) {
        throw new TypeError(`${key}, if provided, must be an Array`);
    }
    return obj[key] || fallback;
}
function checkArray ( obj , key , fallback ) { /* istanbul ignore if */ if ( Object . prototype . hasOwnProperty . call ( obj , key ) && ! Array . isArray ( obj [ key ] ) ) { throw new TypeError ( ` ${ key } ` ) ; } return obj [ key ] || fallback ; }
Ensure that if the key is provided, it must be an array.
@param {Object} obj Object to check with `key`.
@param {string} key Object key to check on `obj`.
@param {*} fallback If obj[key] is not present, this will be returned.
@returns {string[]} Returns obj[key] if it's an Array, otherwise `fallback`
Ensure that if the key is provided it must be an array .