javascript 在 for 循环内部调用异步函数
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Call asynchronous function inside for loop
提问by Ragnis
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
});
}
How can I access the pathvariable, that was passed to fs.lstat function?
如何访问path传递给 fs.lstat 函数的变量？
回答by gnarf
This is a perfect reason to use .forEach()instead of a for loop to iterate values.
这是使用.forEach()而不是 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 );
});
});
Also, you could use a closure like @Aadit suggests:
此外，您可以使用@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
}
回答by Aadit M Shah
Classic problem. Put the contents of the for loop in another function and call it in the loop. Pass the path as a parameter.
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。
回答by Mark Gia Bao Nguyen
Recursion works nicely here (especially if you have some i/o that must be executed in a synchronous manner):
递归在这里工作得很好（特别是如果您有一些必须以同步方式执行的 i/o）：
(function outputFileStat(i) {
var path = paths[i];
fs.lstat(path, function(err, stat) {
console.log(path, stat);
i++;
if(i < paths.length) outputFileStat(i);
});
})(0)
