我似乎无法将参数传递给回调

Question

I've created a working recursive for loop, but it only works if my callback has no arguments. I've tried callback(arguments) and callback(...arguments) .

Thanks for any help you can provide!

 function loopFunc (numOfSteps, callback) { let i = 0; if (i >= numOfSteps) { let i = 0 return } callback() loopFunc(numOfSteps - 1, callback)`enter code here` } 

It works if the callback takes no arguments:

 function noArgsHello() { console.log('hello') } const thisWorks = loopFunc(3, noArgsHello); thisWorks() 

It doesn't work if the callback takes an argument:

 function sayHello (input) { console.log(input) } const thisDoesntWork = loopFunc(3, sayHello('hello'); thisDoesntWork() 

Answer 1

You almost there! It depends what is your goal here, you can use either option:

function loopFunc (numOfSteps, callback) {
let i = 0;

  if (i >= numOfSteps) {
      let i = 0
      return
  }

 callback(numOfSteps)
 loopFunc(numOfSteps - 1, callback);
}

function printExtraStuff(greeting) {
  return (val) => { console.log('greeting ', val)}
}

function printSteps(num) {
    console.log(num);
}

var test1 = function() { loopFunc(3, printExtraStuff('hi there') )};
test1()

var test2 = function() { loopFunc(3, printSteps )};
test2()

Answer 2

In this way:

const thisDoesntWork = loopFunc(3, sayHello('hello');

You are not passing a callback anymore, but you are executing the sayHello function and passing the returned value of that function to the loopFunc .

What you can do in these cases, is to use the bind method of functions for passing the function with arguments:

const thisDoesntWork = loopFunc(3, sayHello.bind(sayHello, 'hello'));

Or you can pass directly a function which executes your sayHello so that the argument is still a function and it will be used as callback inside your loopFunc :

const thisDoesntWork = loopFunc(3, () => sayHello('hello'));

Answer 3

You need to use an anonymous function if you want to pass parameters in an argument -based function ( callback is an argument). Your code should instead be like this:

 function sayHello(input) { console.log(input) } const works = () => sayHello('hello'); works();