フリー問題

問題文

A developer needs a new array holding the length of every name in names, without changing names. Which call satisfies both requirements?

選択肢

1. names.forEach(function (n) { return n.length; }), which collects every returned value into a new array once the iteration has finished.
2. names.map(function (n) { return n.length; }), which returns a new array of the same length and leaves names untouched.
3. names.reduce(function (n) { return n.length; }), which replaces each element with its length in place.
4. names.filter(function (n) { return n.length; }), which returns the length of every name.