// 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 keys(obj).map((prop) => { return obj[prop]; }); }; const mapObject = (obj, cb) => { // Like map for arrays, but for objects. Transform the value of each property in turn. // http://underscorejs.org/#mapObject keys(obj).forEach(prop => (obj[prop] = cb(obj[prop]))); return obj; }; const pairs = (obj) => { // Convert an object into a list of [key, value] pairs. // http://underscorejs.org/#pairs return keys(obj).map((prop) => { return [prop, obj[prop]]; }); }; /* 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 keys(obj).forEach((prop) => { const newProp = obj[prop]; obj[newProp] = prop; delete obj[prop]; }); return obj; }; const defaults = (obj, defaultProps) => { // Fill in undefined properties that match properties on the `defaultProps` parameter object. // Return `obj`. // http://underscorejs.org/#defaults keys(defaultProps).forEach((prop) => { if (Object.prototype.hasOwnProperty.call(obj, prop)) return; obj[prop] = defaultProps[prop]; }); return obj; }; /* eslint-enable no-unused-vars */ module.exports = { keys, values, mapObject, pairs, invert, defaults, };