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How to create a function and pass in variable length argument list?

I want to call the console.log with variable argument list

console.log("a","b")
console.log("a","b","c")

but i get the arguments from an array:

var arr = ["a","b","c"];

and i want to pass as single variables not as a complete array. so console.log(arr) is not what i am looking for,console.log(arr[0],arr[1],arr[2]) is also bad because i dont know the array length ofc.

How can i do that?

the console.log is only an example, i would use this in different problems

UPDATE

How to create a function and pass in variable length argument list? is not good. because according to the answer

function dump(a,b) {
  console.log("a:"+a,"b:"+b);
}

var asd = [1,2,3]

dump.call(this,asd)

should give an output: a:1,b:2 instead of a:[1,2,3] b:undefined

UPDATE:

maybe my question was not clear enough, sorry.

The console.log is only a example of variable argument invoking

i want to use the same method for different problems

look at this example:

function Sum() {
  var temp = 0;
  for(var i=0;i<arguments.length;++i) {
     temp+= arguments[i];
  }
  return temp;
}

and i want to call with different arguments which are in an array.

var test1 = [1,2,3];
var test2 = [4,5,6];

var a = Sum.call(this,test1) //this gives an output "01,2,3"

var b;
for(var i=0;i<test2.length;++i) {
  b = Sum(test2[i])
} //this is also bad because it only returns 6 at the last invoke.
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2
  • It is a duplicate. Both questions are how to pass an array of arguments to a function as separate arguments. Nowhere in the other question or answer is Function.call even mentioned. Do you mean to ask 'why does dump.call(this,asd) result in an output of "a:[1,2,3] b:undefined"?' Commented May 25, 2011 at 20:43
  • 2
    You keep using CALL. Use APPLY. Do Sum.apply(this,test1) and see what you get. Commented May 25, 2011 at 21:02

4 Answers 4

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7

Use Function.apply:

console.log.apply(console, arr);

This answers the question you asked. If you intended to ask:

Why does dump.call(this,asd) result in an output of "a:[1,2,3] b:undefined"?

The answer (which any documentation will tell you) is that Function.call is variadic, and any arguments after the first are passed to the function, whereas Function.apply takes only two arguments: a value for this in the applied function and an array of arguments to pass to the function.

In other words, Function.call is equivalent to:

function (self) {
    var args = [].slice.apply(arguments, [1]);
    return this.apply(self, args)
}
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1 Comment

sorry. i used call instead of apply. im a little tired
3 
console.log.apply(console, [stuffs])

See: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/apply

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2

Based on your update, this modification will work:

function dump(a,b) {
  console.log("a:"+a,"b:"+b);
}

var asd = [1,2,3]

dump.apply(this,asd)

Note that you need to use "apply" rather than "call". But your function is dictating how many arguments to output (console.log("a:"+a,"b:"+b)), so this is of limited value. Can you please try to clearly explain why console.log.apply(console, asd) doesn't give you what you want?

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0

Not sure exactly what you mean... but javascript is a dynamic languange and you can just pass around dynamic objects. So can you just do something like this:

var obj = {0: "a", 1: "b", 2: "c"}; console.log(obj);

The object 'obj' can contain as many properties as you need and can be passed into any function as a single argument.

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