将 Function.prototype.bind 与参数数组一起使用? [英] Using Function.prototype.bind with an array of arguments?

问题描述

如何使用参数数组调用 Function.prototype.bind，而不是硬编码参数?(不使用 ECMA6，所以没有扩展运算符).

How can I call Function.prototype.bind with an array of arguments, as opposed to hardcoded arguments? (Not using ECMA6, so no spread operator).

我正在尝试在使用回调的模块周围放置一个 Promise 包装器，并且我想绑定所有传入我的包装器方法的参数并绑定它们.然后我想用我自己的回调调用部分应用的绑定函数，它将解析或拒绝一个承诺.

I'm trying to put a promises wrapper around a module that uses callbacks and I want to bind all of the arguments passed in to my wrapper method and bind them. Then I want to call the partially applied bound function with my own callback, which will resolve or reject a promise.

var find = function() {
  var deferred, bound;
  deferred = Q.defer();
  bound = db.find.bind(null, arguments);
  bound(function(err, docs) {
    if(err) {
      deferred.fail(err);
    } else {
      deferred.resolve(docs);
    }
  });
  return deferred.promise;
}

但显然这不起作用，因为 bind 需要参数而不是参数数组.我知道我可以通过将回调插入到参数数组的末尾并使用 apply 来做到这一点:

But obviously this doesn't work because bind expects arguments rather than an array of arguments. I know I could do this by inserting my callback onto the end of the arguments array and using apply:

arguments[arguments.length] = function(err, docs) { ... }
db.find.apply(null, arguments);

或者通过迭代参数数组并为每个参数重新绑定函数:

Or by iterating over the arguments array and rebinding the function for each argument:

var bound, context;
for(var i = 0; i < arguments.length; i++) {
   context = bound ? bound : db.find;
   bound = context.bind(null, arguments[i]);
}
bound(function(err, docs) { ... })

但是这两种方法都感觉很脏.有什么想法吗?

But both of these methods feel dirty. Any ideas?

推荐答案

.bind 是一个普通的函数，所以你可以在上面调用 .apply .
您所要做的就是将原始函数作为第一个参数传递，并将所需的 THIS 变量作为参数数组中的第一项:

.bind is a normal function, so you can call .apply on it.
All you have to do is pass the original function as the first param and the desired THIS variable as the first item in the array of arguments:

bound = db.find.bind.apply(db.find, [null].concat(arguments));
//      ^-----^            ^-----^   THIS

这是否可以被认为更清晰由读者决定.

Whether that can be considered cleaner or not is left to the reader.

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