Js basics/core/03 objects

index.js

@@ -1,29 +1,158 @@
-let myVariable;
+// /**
+//  * EXAMPLE 1 - Create object and modify its properties
+//  */
+// let myObject;
 
-console.log(myVariable); // undefined
+// myObject = {
+//   a: 10,
+//   b: "abc"
+// };
 
-myVariable = 10;
+// console.log(myObject);
 
-console.log(myVariable); // 10
+// myObject.a = 15;
 
-myVariable = true;
+// console.log(myObject);
 
-console.log(myVariable); // true
+// myObject.c = true;
 
-myVariable = {
-  x: true,
-  y: 10
-};
+// console.log(myObject);
 
-console.log(myVariable); // {x: true, y: 10}
+// delete myObject.b;
 
-myVariable.y = 20;
+// console.log(myObject);
 
-console.log(myVariable); // {x: true, y: 20}
+// console.log(myObject.a);
 
-// // THIS WILL BREAK THE CODE
-// myVariable = null;
+// /**
+//  * CHALLENGE 1
+//  * 
+//  * Create variable called "myPost".
+//  * Initial value should be {}
+//  * Add property called "postTitle" and value "Object is reference type"
+//  * Add one more property "postLikes" with value 0
+//  * Add third property "shared" and set its value to "false"
+//  * Increase value of the "postLikes" by 1
+//  * Delete property "shared"
+//  */
+// let myPost = {};
 
-myVariable.x = false; // Uncaught TypeError: Cannot set property 'x' of null
+// myPost.postTitle = "Object is reference type";
 
-console.log(myVariable); // {x: false, y: 20}
+// myPost.postLikes = 0;
+
+// myPost.shared = false;
+
+// console.log(myPost);
+
+// myPost.postLikes = myPost.postLikes + 1;
+
+// console.log(myPost);
+
+// delete myPost.shared;
+
+// console.log(myPost);
+
+// /**
+//  * EXAMPLE 2
+//  * 
+//  * Use "const" for object declaration
+//  */
+// const myObject = {};
+
+// myObject.a = true; // NO ERROR! Variable is not reassigned
+
+// console.log(myObject);
+
+// myObject = {
+//   a: true
+// }; // Uncaught TypeError: Assignment to constant variable.
+
+// /**
+//  * CHALLENGE 2
+//  * 
+//  * Create variable "myObject" and add property "a" - 10.
+//  * Create another variable "copyOfMyObject" and its value should be myObject.
+//  * Add new property "b" with value false to the "copyOfMyObject".
+//  * Print to the console "myObject" and "copyOfMyObject" and interpret results.
+//  */
+// let myObject = {
+//   a: 10
+// };
+// let copyOfMyObject = myObject;
+
+// copyOfMyObject.b = false;
+
+// console.log(myObject);
+// console.log(copyOfMyObject);
+
+// /**
+//  * EXAMPLE 3
+//  * 
+//  * Bracket notation
+//  */
+// let myObject = {
+//   a: true,
+//   b: null,
+//   c: 25
+// };
+
+// console.log(myObject["a"]); // true
+
+// // console.log(myObject[a]); // Uncaught ReferenceError: a is not defined
+
+// console.log(myObject["b"]); // null
+
+// const propertyName = "c";
+
+// console.log(myObject[propertyName]); // 25
+
+// console.log(myObject["propertyName"]); // undefined
+
+// myObject["new" + "Property" + "Name"] = "Value for dynamically computed property name";
+
+// console.log(myObject);
+
+// /**
+//  * EXAMPLE 4
+//  * 
+//  * Missing properties
+//  */
+// const myObject = {
+//   a: 3,
+//   b: true
+// };
+
+// // Code execution is not stopped
+// console.log(myObject.c); // undefined
+
+// console.log(myObject.absentProperty); // undefined
+
+// // // Code execution is STOPPED
+// // console.log(nonDeclaredVariable); // Uncaught ReferenceError: nonDeclaredVariable is not defined
+
+// // IMPORTANT!!!
+// // NEVER ASSIGN "undefined" to any property or variable. Use "null" instead
+// myObject.newPropertyWithUndefinedValue = undefined;
+
+// console.log(myObject);
+// console.log(myObject.newPropertyWithUndefinedValue);
+
+// /**
+//  * CHALLENGE 3
+//  * 
+//  * Create object "objectWithNestedObject" with initial value {}.
+//  * Add property "nestedObject" with initial value {}.
+//  * Add property "a" with value "null" to "nestedObject". Use dot notation
+//  * Add property "b" with value "true" to "nestedObject". Use bracket notation. Create new variable with property name
+//  */
+// let objectWithNestedObject = {};
+// objectWithNestedObject.nestedObject = {};
+
+// objectWithNestedObject.nestedObject.a = null;
+
+// const newPropertyName = "b";
+
+// objectWithNestedObject.nestedObject[newPropertyName] = true;
+
+// console.log(objectWithNestedObject);