object ak datastructure hain. jiska use hum data store karne me karte hain.object me data key value ki form me store hoti hian.
Yadi hum same kam array se kar na chahye to kar skte hain. lakin array me humye index mainten kar ne padyegi.index yad kar pana kafi tuff hota hain.isleye hum index ki jgha key ka use karte hain. issye key humasa same rahate hain.par value change ho skte hain.
- Object literal syntax
var obj={
name:"learnjavascript"
}
- object using new key word
var obj=new object();
- annotation
var obj={
name:"learnjavascript"
age:30
}
- dot annotation
var age =obj.age;
var name=obj.name;
- Bracket annotation;
var age = obj['age'];
var name=obj['name'];
Defference between brecket annotation and dot annotation
dot annotation me hum actual key ka name likna hota hain.iske leye hum koi variable etc use nahi kar skte hain.pr brecket annotationme hum variable bhi use kar skte hain. variable ki jo value hogi vo value object ke andr key ke form me search hogi or vahi answer hoga.
- for example:
let obj ={
name:"learnjavascript"
age:20
}
var a ="age";
console.log(obj.age);//correct
console.log(obj.a);// wrong because a name ke koi property nahi hain
console.log(obj["age"]);//correct
console.log(obj['a']);//brecket annotation me a variable ke value age hain.to object me
//age key search hogi na ke a.