Pass variable from array into a function

Question

I have this function:

function getTotal () {
    var args = Array.prototype.slice.call(arguments);
    var total = 0;
    for (var i = 0; i < args.length; i++) {
        total += args[i];
    }

    return total;
}

Lets say that I have an array that is filled with numbers and I do not know the length of it:

var numArray = [ ..., ... ];

How can I call the function getTotal by passing in every element in the numArray as a parameter?

>by passing in every element in the numArray as a parameter? **why** would you do that when you can just pass the array? — Timothy Groote, Aug 11 '17 at 14:46
@TimothyGroote this is not the actual function that I have, just a simplified version of it to focus on this single concept — georgej, Aug 11 '17 at 14:48
Possible duplicate of [Converting an array to a function arguments list](https://stackoverflow.com/questions/1316371/converting-an-array-to-a-function-arguments-list) — H77, Aug 11 '17 at 14:51

Commercial Suicide · Answer 1 · 2017-08-11T14:48:21.257

5

In ES6 you can do this:

getTotal(...numArray);

It called Spread syntax. For more info: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator

edited Aug 11 '17 at 14:48

answered Aug 11 '17 at 14:46

Commercial Suicide

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Oh, sorry, i'll update the answer with EN version =) – Commercial Suicide Aug 11 '17 at 14:47
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator – Timothy Groote Aug 11 '17 at 14:47
This syntax KICKS ASS, ty for mentioning it instead standard apply pattern – DanteTheSmith Aug 11 '17 at 15:12

score 4 · Answer 2 · answered Aug 11 '17 at 14:50

You can call the function using Function.prototype.apply. It will pass the Array as arguments to your function.

function getTotal () {
    var args = Array.prototype.slice.call(arguments);
    var total = 0;
    for (var i = 0; i < args.length; i++) {
        total += args[i];
    }

    return total;
}

var numArray = [1,2,3,4];

console.log( getTotal.apply( null, numArray ) );

Keep in mind you have a typo in your for loop. Should be args.length, instead of arg.length.

score 1 · Answer 3 · answered Aug 11 '17 at 15:08

1

Please try this. Hope it helps

var sum = [1, 2, 3, 4, 5].reduce(add, 0);

function add(a, b) {
    return a + b;
}

answered Aug 11 '17 at 15:08

score 0 · Answer 4 · edited Aug 11 '17 at 17:22

0

Why not just do this:

function getTotal (args) {
    var total = 0;
    for (var i = 0; i < args.length; i++) {
        total += args[i];
    }

    return total;
}

var numArray = [1,2,3];
console.log(getTotal(numArray)); //6

edited Aug 11 '17 at 17:22

Jerry Stratton

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answered Aug 11 '17 at 14:54

Santosh Sapkota

140
5

score 0 · Answer 5 · answered Aug 11 '17 at 15:03

0

If you use the spread operator, you may also want to ES6ify your code:

function getTotal(...vals){
  return vals.reduce((a,b)=>a+b,0);
}

getTotal(...[1,2,4]);

answered Aug 11 '17 at 15:03

Jonas Wilms

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Spread is not an operator, see https://stackoverflow.com/q/37151966/. Note that `...vals` parameter at `function getTotal(...vals){}` is rest element, not spread element – guest271314 Aug 11 '17 at 15:06

Pass variable from array into a function

5 Answers5