// Complete the following underscore functions. // Reference http://underscorejs.org/ for examples. const keys = (obj) => { // Retrieve all the names of the object's properties. // Return the keys as strings in an array. // Based on http://underscorejs.org/#keys return Object.keys(obj); }; const values = (obj) => { // Return all of the values of the object's own properties. // Ignore functions // http://underscorejs.org/#values return Object.keys(obj).map(key => obj[key]); }; const mapObject = (obj, cb) => { // Like map for arrays, but for objects. Transform the value of each property in turn. // http://underscorejs.org/#mapObject Object.keys(obj).forEach((key) => { obj[key] = cb(obj[key]); }); return obj; }; const pairs = (obj) => { // Convert an object into a list of [key, value] pairs. // http://underscorejs.org/#pairs return Object.keys(obj).map((key) => { return [key, obj[key]]; }); }; /* STRETCH PROBLEMS */ const invert = (obj) => { // Returns a copy of the object where the keys have become the values and the values the keys. // Assume that all of the object's values will be unique and string serializable. // http://underscorejs.org/#invert const newObj = {}; Object.keys(obj).forEach((key) => { newObj[obj[key]] = key; }); return newObj; }; const defaults = (obj, defaultProps) => { // Fill in undefined properties that match properties on the `defaultProps` parameter object. // Return `obj`. // http://underscorejs.org/#defaults Object.keys(defaultProps).forEach((key) => { if (obj[key] === undefined) { obj[key] = defaultProps[key]; } }); return obj; }; /* eslint-enable no-unused-vars */ module.exports = { keys, values, mapObject, pairs, invert, defaults, };