在for循环中调用异步函数

Question

var path;

for (var i = 0, c = paths.length; i < c; i++)
{
    path = paths[i];

    fs.lstat(path, function (error, stat)
    {
        console.log(path); // this outputs always the last element
    });
}

如何访问path传递给fs.lstat函数的变量？

Answer 1

这是使用.forEach()for循环来迭代值的完美理由.

paths.forEach(function( path ) {
  fs.lstat( path, function(err, stat) {
    console.log( path, stat );
  });
});

此外,您可以使用像@Aadit建议的闭包:

for (var i = 0, c = paths.length; i < c; i++)
{
  // creating an Immiedately Invoked Function Expression
  (function( path ) {
    fs.lstat(path, function (error, stat) {
      console.log(path, stat);
    });
  })( paths[i] );
  // passing paths[i] in as "path" in the closure
}

Answer 2

经典问题.将for循环的内容放在另一个函数中并在循环中调用它.将路径作为参数传递.