Backbone Collection：迭代和搜索有效

Question

我有什麼：我正在寫我的非常小的媒體播放器。所以我在其中的某個地方收集了字幕（假設每部電影大約有2千個）。因此，每個字幕的樣子：

Object { 
    id: "1" 
    startTime: 2468 
    endTime: 4743 
    text: "Test subtitle." 
} 

我想：非常有效地做兩件事情：

1. .next()方法，它應該得到我的下一個字幕。
2. .getByTime(neededTime)這使得像二進制搜索整個字幕集合有效的方式。重點在於neededTime可能是startTime和endTime屬性（即3000）之間的某種東西。

問題：我要去使用骨幹收集我的字幕，但將如何處理這兩個要求是什麼？我的意思是也許最好是手動實現迭代器模式和二進制搜索？

Answer 1

不知道它是否是最好的解決辦法，但我結束：

if (!Number.isInteger) { 
    Number.isInteger = function isInteger (nVal) { 
     return typeof nVal === "number" && isFinite(nVal) && nVal > -9007199254740992 && nVal < 9007199254740992 && Math.floor(nVal) === nVal; 
    }; 
} 

/** 
* Model 
*/ 
var Subtitle = Backbone.Model.extend({ 
    defaults: { 
     'startTime': '', 
     'endTime': '', 
     'text': '' 
    }, 

    validate: function(attrs) { 
     if (!this.get('startTime')) return 'You missed startTime'; 
     if (!this.get('endTime')) return 'You missed endTime'; 
     if (!this.get('text')) return 'You missed text'; 
     if (this.get('startTime') > this.get('endTime')) return 'startTime cannot be greater than endTime'; 
    }, 

    /** 
    * Compare two time periods 
    * @param that Subtitle with which we compare the current one 
    * @returns {number} positive if {@code this} is greater than {@code that}, negative if {@code this} is less than {@code that} 
    * and zero if they are equals or overlaps or one time period contains another. 
    */ 
    equals: function(that) { 
     if (!(that instanceof Subtitle)) throw Error('Cannot compare with element that does not belong to Subtitle type'); 
     if (this.get('startTime') > that.get('endTime')) return 1; 
     else if (that.get('startTime') > this.get('endTime')) return -1; 
     else return 0; 
    }, 

    /** 
    * 
    * @param moment moment for which we need to find a time period 
    * @returns {number} positive if {@code moment} belongs to time period greater than {@code this}, 
    * negative if {@code moment} belongs to time period less than {@code this} 
    * and zero if the curect time period contain the {@code moment}. 
    */ 
    containMoment: function(moment) { 
     if (!Number.isInteger(moment)) throw Error('Moment should be an Integer'); 

     if (moment >= this.get('startTime') && moment <= this.get('endTime')) return 0; 
     else if (moment < this.get('startTime')) return -1; 
     else if (moment > this.get('endTime')) return +1; 
     else throw Error('Impossible case :-)'); 
    } 
}); 

/** 
* Collection 
*/ 
var Subtitles = Backbone.Collection.extend({ 
    model: Subtitle, 
    index: 0, 

    next: function() { 
     return this.at(this.index++); 
    }, 

    getByMoment: function(moment) { 
     return this._binarySearch(this.toArray(), moment); 
    }, 

    _binarySearch: function(array, moment) { 
     'use strict'; 

     var minIndex = 0; 
     var maxIndex = array.length - 1; 
     var currentIndex; 
     var currentElement; 

     while (minIndex <= maxIndex) { 
      currentIndex = (minIndex + maxIndex)/2 | 0; 
      currentElement = array[currentIndex]; 

      if (currentElement.containMoment(moment) > 0) { 
       minIndex = currentIndex + 1; 
      } 
      else if (currentElement.containMoment(moment) < 0) { 
       maxIndex = currentIndex - 1; 
      } 
      else { 
       return array[currentIndex]; 
      } 
     } 

     throw Error('No subtitle for this moment'); 
    } 
}); 

/** 
* Test 
*/ 
var data = [ 
    { id: '1', 
    startTime: 2468, 
    endTime: 4743, 
    text: 'Here\'s little Ben nodding off.' }, 
    { id: '2', 
    startTime: 5389, 
    endTime: 7698, 
    text: 'Look at Aunt Monica\'s Little boy.' }, 
    { id: '3', 
    startTime: 7948, 
    endTime: 11099, 
    text: '-Look, he\'s got Ross\' hair cut.\n-Let me see.' }, 
    { id: '4', 
    startTime: 11948, 
    endTime: 14907, 
    text: 'Oh, God!\nIs he just the sweetest thing?' }, 
    { id: '5', 
    startTime: 15148, 
    endTime: 17946, 
    text: 'You must just want\nto kiss him all over.' } 
]; 
var subtitles = new Subtitles(); 
subtitles.add(data); 

var moment = 3000; 
console.log(subtitles.next().attributes); 
console.log(subtitles.next().attributes); 
console.log(subtitles.next().attributes); 
console.log(subtitles.next().attributes); 
console.log(subtitles.getByMoment(moment).attributes);