Three ways to create objects in JS

Catalog

Three ways to create objects

Literal creation

utilize new Object() Create objects

Using constructors to create objects

Traversing objects and methods

The difference between variable attributes

The difference between function and method

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An object is an unordered collection of related properties and methods

Three ways to create objects

Literal creation

var stu = {
                name: ' Xiao Ming ',
                age: 12,
                study: function() {
                    console.log(' I'm learning ');
                }
            }

1. Objects are stored in key value pairs , key Property name ： value Property value .

2. Multiple attributes or methods are separated by commas .

3. There are two ways to use the properties in an object

object . Property name And the object .[' Property name '], The second method must be quoted .

console.log(stu.name);
console.log(stu['age']);

4. Method of calling object

object . Method （）

stu.study();

utilize new Object() Create objects

Use the equal sign assignment method to add the properties and methods of the object .

Each property and method is separated by a semicolon .

  var obj = new Object();
        obj.name = ' Xiaohong ';
        obj.age = 13;
        obj.study = function() {
            console.log(" Xiao Hong is studying ");
        }
        obj.study();

Using constructors to create objects

The first two methods can only create objects once at a time , It takes a lot of code , trouble . We can use the method of function , Load the same code , Encapsulate these objects , Is to abstract out the same attributes and methods in the object , Encapsulate it in a function .

1. The constructor name is capitalized , amount to java Class name in .

2. The constructor must write this, Otherwise, multiple object points will be confused , I can't tell who is who .

3. To create an object, add new Constructor name （）

  function Star(name, age, sex) {
            this.name = name;
            this.age = age;
            this.sex = sex;
            this.print = function(write) {
                console.log(write);
            }
        }
        var obj1 = new Star(' Xiaohong ', 24, ' Woman ', ' Write ');
        var obj2 = new Star(' Xiao Ming ',12,' male ');
        obj1.print(' Write ');
        console.log(obj1);

Traversing objects and methods

for( Variable  in object ）{}

k It's a variable. , If traversal k What you get is the attribute name ,stu[k] What you get is the attribute value . It doesn't need to be in there 1 Put quotes , because k It's a variable .

  var stu = {
            name: ' Xiao Ming ',
            age: 12,
            study: function() {
                console.log(' I'm learning ');
            }
        }
        for(k in stu){
            console.log(k);
        }
        for (k in stu) {
            console.log(stu[k]);
        }

The difference between variable attributes

Variables are declared and assigned separately , When using, write the variable name directly , Exist alone

The attribute is inside the object , No declaration required , But when you use it, you must use the object . attribute

The difference between function and method

What's outside is called a function , The method in the object is called , What they have in common is to realize some function and do something

Functions are declared separately , Direct function name when calling （） Exist alone

Method is inside the object , When called, the object . Method （）.