javascript - Is it possible to spread the input array into arguments? - Stack Overflow

admin管理员组

文章数量:1279148

So Promise.all passes an array as a value into the function, I would much rather it pass the array values as arguments.

Assume I have this function:

function printData(a,b,c){
   console.log(a,b,c)
}

I would like

Promise.all([1,2,3]).then(printData)
>> [1,2,3] undefined undefined

To print this instead

>> 1 2 3

Is there a better way of doing this:

Promise.all([1,2,3,4]).then(function(values){printData.apply(null, values)})

using the spread operator?

I also tried

Promise.all([1,2,3]).then(printData.apply)

But it returns an error

So Promise.all passes an array as a value into the function, I would much rather it pass the array values as arguments.

Assume I have this function:

function printData(a,b,c){
   console.log(a,b,c)
}

I would like

Promise.all([1,2,3]).then(printData)
>> [1,2,3] undefined undefined

To print this instead

>> 1 2 3

Is there a better way of doing this:

Promise.all([1,2,3,4]).then(function(values){printData.apply(null, values)})

using the spread operator?

I also tried

Promise.all([1,2,3]).then(printData.apply)

But it returns an error

• javascript
• ecmascript-6
• promise

Share Improve this question Follow edited Feb 17, 2017 at 19:50 lonewarrior556 asked Feb 17, 2017 at 18:05 lonewarrior556lonewarrior556 4,50922 gold badges3232 silver badges5858 bronze badges

Add a ment  | 

4 Answers 4

Sorted by: Reset to default 9

One way using ES 6 Destructuring

function printData(a,b,c){
   console.log(a,b,c)
}

Promise.all([1,2,3]).then( data => {var [a,b,c] = data;
                           printData(a,b,c);});

Using ES 6 Spread Syntax

function printData(a,b,c){
   console.log(a,b,c)
}

Promise.all([1,2,3]).then(data => printData(...data))

Instead of

.then(printData)

you can spread with

.then(args => printData(...args))

Trying to use the spread operator technically has you nesting functions, which works, but there is another way

Promise.all([1,2,3]).then(printData.apply)

Doesn't work because this is equal to:

printData.apply.call(undefined, [1,2,3])

which returns the same error

>>Uncaught TypeError: Function.prototype.apply was called on undefined,
 which is a undefined and not a function

---

Promise passes this in to call and it loses track of what it should be. What you want is:

test.apply.call(test,[null,1,2,3])

which equals:

test.apply(null,[1,2,3])

which equals

test(1,2,3)

because you don't have control over Promise using call, use bind to determine the arguments

printData.apply.bind(printData, null)

which when called equals

printData.apply.bind(printData, null).call(undefined, [1,2,3])
>> 1 2 3

so Finally:

Promise.all([1,2,3]).then(printData.apply.bind(printData,null))
>> 1 2 3

Here's a related question about bining apply and call Why can I not call a function.apply?

function printData(...a){
  console.log(a.reduce((n,o)=>n.concat(o),[]).join(","));
}

Take all arguments, reduce all Arrays in Arrays to one Array, pass it as arguments to console.log.

http://jsbin./vutizahago/edit?console

本文标签： javascriptIs it possible to spread the input array into argumentsStack Overflow