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objects.js
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82 lines (72 loc) · 2.18 KB
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// 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)).slice();
};
const values = (obj) => {
// Return all of the values of the object's own properties.
// Ignore functions
// http://underscorejs.org/#values
return Object.values(obj);
};
const mapObject = (obj, cb) => {
// Like map for arrays, but for objects. Transform the value of each property in turn.
// http://underscorejs.org/#mapObject
const newObj = {};
const objKeys = keys(obj);
for (let i = 0; i < objKeys.length; i++) {
const key = objKeys[i];
newObj[key] = cb(obj[key]);
}
return newObj;
};
const pairs = (obj) => {
// Convert an object into a list of [key, value] pairs.
// http://underscorejs.org/#pairs
const keyArr = Object.keys(obj);
const valArr = Object.values(obj);
let newArray = [];
const bigArray = [];
for (let i = 0; i < keyArr.length; i++) {
newArray.push(keyArr[i], valArr[i]);
bigArray.push(newArray);
newArray = [];
}
return bigArray;
};
/* 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 keyArr = Object.keys(obj);
const valArr = Object.values(obj);
const newObj = {};
for (let i = 0; i < keyArr.length; i++) {
newObj[valArr[i]] = keyArr[i];
}
return newObj;
};
const defaults = (obj, defaultProps) => {
// Fill in undefined properties that match properties on the `defaultProps` parameter object.
// Return `obj`.
// http://underscorejs.org/#defaults
const defaultKeys = keys(defaultProps);
for (let i = 0; i < defaultKeys.length; i++) {
if (obj[defaultKeys[i]] === undefined) {
obj[defaultKeys[i]] = defaultProps[defaultKeys[i]];
}
} return obj;
};
/* eslint-enable no-unused-vars */
module.exports = {
keys,
values,
mapObject,
pairs,
invert,
defaults,
};