如何将JS变量的值（而不是引用）传递给函数？

问题描述

这里是我想要运行的一个简化版本：

Here is a simplified version of something I'm trying to run:

for (var i = 0; i < results.length; i++) {
    marker = results[i];
    google.maps.event.addListener(marker, 'click', function() {
        change_selection(i);
    });
}

但我发现每个监听器使用results.length当for循环终止时的值）。如何添加侦听器，使得每个在使用i的值时添加它，而不是对i的引用？

but I'm finding that every listener uses the value of results.length (the value when the for loop terminates). How can I add listeners such that each uses the value of i at the time I add it, rather than the reference to i?

推荐答案

您需要创建一个单独的作用域，通过将变量作为函数参数传递将其保存为当前状态： p>

You need to create a separate scope that saves the variable in its current state by passing it as a function parameter:

for (var i = 0; i < results.length; i++) {
  (function (i) {
    marker = results[i];
    google.maps.event.addListener(marker, 'click', function() {
      change_selection(i);
    });
  })(i);
}

通过创建一个匿名函数并使用变量作为第一个参数调用它，你将传递给函数并创建一个闭包。

By creating an anonymous function and calling it with the variable as the first argument, you're passing-by-value to the function and creating a closure.

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