javascript - 使用 JavaScript 跟踪对象键的有效方法

Question

我正在使用带有陷阱的 Proxy 对象来跟踪对象键，这样我就可以轻松地迭代和/或从对象中选择一个随机键，而性能开销很小。目前，我将添加的键存储在数组中。这对于插入和随机选择非常有效，但是当删除一个属性时，开销很大:

// Benchmark
var testObject = createProxy();

var start = performance.now();

for( var i = 0; i < 1e4; i++ )
  testObject[Math.random() * 1e6 << 0] = true;
for( var i in testObject )
  if( i[0] !== '_' )
    delete testObject[ i ];
    
var end = performance.now();

var total = ( end - start );
console.log( 'Test took ' + total + ' ms' );

// Implementation
function createProxy() {
  function keyTracker() {
    const set = new Set();
    function defineProperty( target, property, descriptor ) {
      target[property] = descriptor.value;
      if( property[0] === '_' ) return true;
      if( set.has( property ) ) return true;
      
      set.add( property );
      target[ '__keys' ].push( property );
      return true;
    }
    function deleteProperty( target, property ) {
      if( property[ 0 ] === '_' ) return true;
      
      delete target[ property ];
      if( !set.delete( property ) ) return true;
      
      target[ '__keys' ] = target[ '__keys' ].filter( 
        key => key !== property
      );
      return true;
    }
    return { defineProperty, deleteProperty };
  }
  
  var proxy = new Proxy(
    Object.defineProperty( {}, '__keys', {
     configurable: true,
     enumerable: false,
     writable: true,
     value: []
  } ), keyTracker() );
  
  return proxy;
}

调用 Array.filter() 会随着对象中键的数量增长而呈指数增长。我正在寻找一种解决方案，让我不必调用它来删除单个元素。

有没有一种方法可以重新构建它以允许 O(1) 插入、随机选择和删除 key ？

Answer 1

您可以只使用拼接。它会让您的时间缩短 800-1000 毫秒。

       target[ '__keys' ].splice(target[ '__keys' ].indexOf(property), 1);

// Benchmark
var testObject = createProxy();

var start = performance.now();

for( var i = 0; i < 1e4; i++ )
  testObject[Math.random() * 1e6 << 0] = true;
for( var i in testObject )
  if( i[0] !== '_' )
    delete testObject[ i ];
    
var end = performance.now();

var total = ( end - start );
console.log( 'Test took ' + total + ' ms' );

// Implementation
function createProxy() {
  function keyTracker() {
    const set = new Set();
    function defineProperty( target, property, descriptor ) {
      target[property] = descriptor.value;
      if( property[0] === '_' ) return true;
      if( set.has( property ) ) return true;
      
      set.add( property );
      target[ '__keys' ].push( property );
      return true;
    }
    function deleteProperty( target, property ) {
      if( property[ 0 ] === '_' ) return true;
      
      delete target[ property ];
      if( !set.delete( property ) ) return true;
      
      target[ '__keys' ]
      .splice(target[ '__keys' ].indexOf(property), 1);
      return true;
    }
    return { defineProperty, deleteProperty };
  }
  
  var proxy = new Proxy(
    Object.defineProperty( {}, '__keys', {
     configurable: true,
     enumerable: false,
     writable: true,
     value: []
  } ), keyTracker() );
  
  return proxy;
}