[Immutable.js] Lightning Fast Immutable.js Equality Checks with Hash Codes-优快云博客

本文探讨了使用Immutable.js库中的哈希码进行快速迭代器相等性检查的方法。通过比较不同迭代器的内容生成的哈希码来确认它们是否相等，这种方法虽然高效但存在一定的碰撞风险。

While Immutable.js offers .is() to confirm value equality between iterables it comes at the cost of referencing each key and value in both objects. For lightning fast equality checks, Immutable.js can produce a hash code based on an iterable's content. If two iterables have the same content, their hash codes will be the same. It's worth noting that this technique is unsuitable for mission critical application development since there is a chance, however slight, that checksums like these might collide. This is outlined here: https://en.wikipedia.org/wiki/Collision_(computer_science)

mocha.setup('bdd');
const expect = chai.expect;

class Todo {
  
  constructor(title="", items=Immutable.List(), completed=false) {
    this.id = (+new Date() + Math.floor(Math.random() * 999999)).toString(36);
    this.title = title;
    this.items = items;
    this.completed = completed;
  }
  
}

function generateTodos() {
  
  const todos = []
  
  _.each(_.range(5), index => {
    var todo = new Todo(`Todo ${index}`);
    
    todo.completed = Math.round(Math.random()) === 0;
      
    _.each(_.range(Math.floor(Math.random()*100)), index => {
      todo.items = todo.items.push(`Item ${index}`);
    });
    
    todos.push(todo);
      
  });
  
  return todos;
}

describe('Lightning Fast Equality checks with Hash Codes', () => {
  
  it('should take separate lists with the same items and see equal hash codes', () => {

    var todos = generateTodos();
    
    let todos1 = Immutable.List.of(...todos);
    let todos2 = Immutable.List.of(...todos);

    expect(todos1).to.not.equal(todos2);
    expect(todos1.hashCode()).to.equal(todos2.hashCode());

  });
  
});

mocha.run();