Adding six exercises working with objects

prework/8_ObjectsChallenges.js

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+// Week 3 - Objects
+
+// In the following exercises, you will need to place your code or answer underneath each
+// exercise prompt.
+
+// First try answering these without using references or looking up any information.
+// Then, check your answer by using references and/or running your code.
+// You can run your JS code using the Chrome or Firefox Developer tools, or by using Node.js or using Replit.com 
+// Feel free to update your answers if you got them wrong at first -- this exercise is for your own learning.
+// But make sure you understand why the correct answer is right.
+
+// Exercise 1. Write a function called keys, which accepts an object and returns an array of all of the keys in the object.
+// IMPORTANT: Do not use the built in Object.keys() function!
+// Examples:
+// let obj = { a: 1, b: 2, c: 3 };
+// keys(obj); // ["a", "b", "c"]
+// let obj2 = { first: 'Matt', last: 'Lane' };
+// keys(obj2); // ["first", "last"]
+// let obj3 = {};
+// keys(obj3); // []
+
+
+// Exercise 2. Write a function called values, which accepts an object and returns an array of all of the values in the object.
+// IMPORTANT: Do not use the built in Object.values() function!
+// Examples:
+// let obj = { a: 1, b: 2, c: 3 };
+// values(obj); // [1,2,3]
+// let obj2 = { first: 'Matt', last: 'Lane', isDogOwner: true };
+// values(obj2); // ["Matt", "Lane", true]
+// let obj3 = {};
+// values(obj3); // []
+
+// Exercise 3. Write a function called entries, which accepts an object and returns an array of arrays of key-value pairs.
+// In other words, each sub-array is an "entry" in the object with two elements: the first element is the key, and the second element is the value.
+// IMPORTANT: Do not use the built in Object.entries() function!
+// Examples:
+// let obj = { a: 1, b: 2, c: 3 };
+// entries(obj);
+// [["a",1], ["b",2], ["c",3]]
+// let obj2 = { first: 'Matt', last: 'Lane', isDogOwner: true };
+// entries(obj2);
+// [["first","Matt"], ["last","Lane"], ["isDogOwner",true]]
+// let obj3 = {};
+// entries(obj3); // []
+
+// Exercise 4. Write a function called pluck, which takes an array of objects and the name of a key.
+// The function should return an array containing the value associated with that key for each object, or undefined if that key is not present in the object.
+// Examples:
+// pluck([{ name: "Tim" }, { name: "Matt" }, { name: "Elie" }],'name')
+// ["Tim", "Matt", "Elie"]
+// pluck([{ name: "Tim", isBoatOwner: true }, { name: "Matt", isBoatOwner: false }, { name: "Elie" }],'isBoatOwner')
+// [true, false, undefined]
+
+// Exercise 5. Write a function called stringFromObject that generates a string from an object's key/value pairs.
+// The format should be "key = value, key = value".
+// Each key/value pair should be separated by a comma and space except for the last pair.
+// Examples:
+// stringFromObject({ a: 1, b: '2' });
+// "a = 1, b = 2"
+// stringFromObject({ name: 'Elie', job: 'Instructor', isCatOwner: false });
+// "name = Elie, job = Instructor, isCatOwner = false"
+// stringFromObject({}); // ""
+
+// Exercise 6. Write a function called minMaxKeyInObject that accepts an object with numeric keys.*
+// The function should return an array with the following format: [lowestKey, highestKey]
+// Examples:
+// minMaxKeyInObject({ 2: 'a', 7: 'b', 1: 'c', 10: 'd', 4: 'e' });
+// [1, 10]
+// minMaxKeyInObject({ 1: 'Elie', 4: 'Matt', 2: 'Tim' });
+// [1, 4]
+
+
+