有什么快速的方法来获得< option>从< select>按价值，使用JavaScript？ [英] Is there any fast way to get an <option> from a <select> by value, using JavaScript?

问题描述

我有一个< select> ;.使用JavaScript，我需要获得一个特定的< option>从选项列表中，我所知道的是选项的价值。这个选项可能会也可能不会被选中。

这里有一个问题：有成千上万个选项，我需要循环执行几百次。现在我循环访问options数组并查找我想要的选项。这太慢了（在我的速度非常快的机器上，浏览器被锁定，直到我在几分钟后杀死它）。

有没有更快的方法可以做这个？我会采取特定于浏览器的方式，但当然一个DOM标准的方式会很好。 它是这样的：

  //首先，构建反向查找
 var optCount = mySelect.options.length; 
 var reverseLookup = {}; 
 for（var i = 0; i< optCount; i ++）
 {
 var option = mySelect.options [i]; 
 if（！reverseLookup [option.value]）
 {
 //使用一个数组来解释具有相同值的多个选项
 reverseLookup [option.value] = [] ; 
} 
 //存储对DOM元素的引用
 reverseLookup [option.value] .push（option）; 
} 
 
 //然后，使用它来查找选项
 var foundOptions = reverseLookup [您要查找的值]; 
 if（foundOptions& foundOptions.length）
 {
 alert（foundOptions [0] .id）; 
} 
  

I have a <select>. Using JavaScript, I need to get a specific <option> from the list of options, and all I know is the value of the option. The option may or may not be selected.

Here's the catch: there are thousands of options and I need to do this a few hundred times in a loop. Right now I loop through the "options" array and look for the option I want. This is too slow (in the sense that on my very fast machine the browser locked up until I killed it after a few minutes).

Is there any faster way to do this? I'll take browser-specific ways, but of course a DOM-standard way would be nice.

解决方案

I'd do it like this:

// first, build a reverse lookup
var optCount      = mySelect.options.length;
var reverseLookup = {};
for (var i = 0; i < optCount; i++)
{
  var option = mySelect.options[i];
  if (!reverseLookup[option.value])
  {
    // use an array to account for multiple options with the same value
    reverseLookup[option.value] = [];
  }
  // store a reference to the DOM element
  reverseLookup[option.value].push(option);
}

// then, use it to find the option
var foundOptions = reverseLookup["Value that you are looking for"];
if (foundOptions && foundOptions.length)
{
  alert(foundOptions[0].id);
}

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