Manipulate Object

Briefly describe how to handle objects (Array Objects).

Values with object data types have different data access methods than raw values, and JavaScript basically provides a variety of built-in functions that handle values.

Object

Object can declare zero or more key value pairs enclosed by {}. The key value pair is defined in the form of [Key]:[Value], and the key becomes the property of the Object. [Object Name] if you are accessing the value.You can access it in the form of [key]. Returns the undefined value if accessed with a key that does not exist.

const emptyObject = {}; // Object with no data
const cube = { title: "cube(123)", color: "red" };
 
console.log(emptyObject.title); // undefined
console.log(cube.title); // cube(123)

You can also change the value of an already created object or add/remove new properties.

const emptyObject = {};
const cube = { title: "cube(123)", color: "red" };
 
cube.color = "blue";
emptyObject.color = "yellow";
 
delete cube.title;
 
console.log(cube.color); // blue
console.log(emptyObject.color); // yellow
console.log(cube.title); // undefined

Array Object

Array Object can declare zero or more values enclosed by []. To access the value, you must access it through index. index refers to the location in the Array Object where a specific value exists. index is an integer that starts with zero. You can access the values in the same way as [ArrayObject][index].

const emptyArray = []; // Array with no data
const cubes = ["cube0", "cube1", "cube2"];
 
console.log(emptyArray[0]); // undefined
console.log(cubes[0]); // cube0
console.log(cubes[2]); // cube2

You can change the value of an array object that has already been created, add/remove new values, and access the included length property by default to know the number of values in the array object.

const emptyArray = [];
const cubes = ["cube0", "cube1", "cube2"];
 
emptyArray[0] = "value0";
cubes[0] = "cube3";
 
console.log(emptyArray[0]); // value0
console.log(cubes[0]); // cube3
console.log(cubes.length); // 3

The various functions that manipulate the data in Array Object can be found in the following documents.

JavaScript Array Methods