hasOwnProperty和对象的属性访问

Question

I have very simple question.Is there any performance relation about accessing object's properties like object[property] and the number of properties ?? Is there some internal loop or something , same question about hasOwnProperty - any loops or just direct access like array[index] ??

Answer 1

JavaScript is a dynamic programming language: properties can be added to, and deleted from, objects on the fly. This means an object's properties are likely to change. Most JavaScript engines use a dictionary-like data structure as storage for object properties - each property access requires a dynamic lookup to resolve the property's location in memory. This approach makes accessing properties in JavaScript typically much slower than accessing instance variables in programming languages like Java and Smalltalk. In these languages, instance variables are located at fixed offsets determined by the compiler due to the fixed object layout defined by the object's class. Access is simply a matter of a memory load or store, often requiring only a single instruction.

use V8 (JavaScript engine) for better performance.