javascript: pass an array to a function

Question

here is my javascript code:

var my_array = new Array();
my_array[0] = "a";
my_array[0] = "b";
my_array[0] = "c";

print_array(my_array);

function print_array(arr)
{
   alert(arr);
}

But it doesn't work, because I can't pass the array to the function. So, how can I pass an entire array to javascript function?

EDIT: Nevermind. I found the solution.
Hidden cause this is bad practice and passes the array as a string:

If someone will need to pass an array to the function, first use this: JSON.stringify() and javascript will be able to parse an array.

score 9 · Answer 1 · answered Oct 27 '12 at 01:15

9

The problem is you are assigning each element to index 0, so they are overwriting each other.

// should be
my_array[0] = "a";
my_array[1] = "b";
my_array[2] = "c";

// alternatively, if you don't want to track the index
my_array.push("a");
my_array.push("b");
my_array.push("c");

The rest of the code looks fine. You can pass whole arrays, or any object for that matter to a function in exactly the manner you have shown in your code.

When you alert it, javascript will concatenate the array into a comma separated string for easy viewing.

answered Oct 27 '12 at 01:15

Billy Moon

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1

or `my_array.push("a", "b", "c")` – roberkules Oct 27 '12 at 01:19
1

@roberkules: I like that one, I think you deserve a prize for that. – Billy Moon Oct 27 '12 at 01:23
@roberkules the problem with it is that it is less efficient, and harder to discern the meaning of. I do like to split strings by spaces in this way if there is a long list of options, or something that is easier to read as a unit, but only when efficiency is not important (which is actually most of the time for me in javascript). – Billy Moon Oct 27 '12 at 01:31
Maybe that's why you can see it often in libraries. There it's most likely only parsed once and then the array exists the whole time. So performance shouldn't be an issue. And if I use such an array definition I only parse it once. – roberkules Oct 27 '12 at 01:35
let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/18648/discussion-between-billy-moon-and-roberkules) – Billy Moon Oct 27 '12 at 01:41
Just posting the link from the chat - a better performance comparison: http://jsperf.com/array-vs-split-3 – roberkules Oct 27 '12 at 02:08

score 2 · Answer 2 · answered Oct 27 '12 at 01:14

2

Try this code instead:

function print_array(arr)
{
   alert(arr);
}

var my_array = new Array();
my_array[0] = "a";
my_array[1] = "b";
my_array[2] = "c";

print_array(my_array);

You should define a function before you can call it as a good programming practice.

Also note the order of your elements that are being assigned, you're putting everything on 0, and they should be on 1, 2 etc.

answered Oct 27 '12 at 01:14

jcolebrand

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Not in JS you don't. Functions are hoisted. – David G Oct 27 '12 at 01:15
Good point David, hoisting. Forgot that. Updated to make it about a good business practice. – jcolebrand Oct 27 '12 at 01:17
you only have to define the function before you call it, when it is assigned to a variable like so: `var myFunc = function(){ alert(123) }` – Billy Moon Oct 27 '12 at 01:17

score 1 · Answer 3 · edited May 23 '17 at 12:34

1

To extend Billy Moon's answer

You can define your array like this:

my_array = ["a", "b", "c"];

And like this:

my_array = [];
my_array[0] = "a";
// ...

edited May 23 '17 at 12:34

Community

1
1

answered Oct 27 '12 at 01:18

Andreas Louv

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123

roberkules · Answer 4 · 2012-10-27T01:23:41.547

0

var my_array = ["a", "b", "c"];
// or a popular way to define (mainly string) arrays:
var my_array = "abc".split("");

print_array(my_array);

function print_array(arr) {
   alert(arr);
}

edited Oct 27 '12 at 01:23

answered Oct 27 '12 at 01:17

roberkules

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Why it's that a popular way to define such arrays and what does it do. How come `a = "123".split("");console.log(a[0]+a[2])` gives 13? – Andreas Louv Oct 27 '12 at 01:20
okay, so it's a popular way (I see it in many js libraries) to define arrays of strings. – roberkules Oct 27 '12 at 01:23

codingbiz · Answer 5 · 2012-10-27T01:22:59.223

0

You were using the same index 0

var my_array = new Array();
my_array[0] = "a";
my_array[1] = "b";
my_array[2] = "c";

JS Fiddle

edited Oct 27 '12 at 01:22

answered Oct 27 '12 at 01:17

codingbiz

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score 0 · Answer 6 · answered Nov 09 '22 at 02:35

0

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


function print_array(arr)
{
   alert(arr);
}

print_array(my_array);

answered Nov 09 '22 at 02:35

Fauzan DP

51
4

1

Its always best if you explain the answer. – Rohit Gupta Nov 10 '22 at 08:51

score -2 · Answer 7 · answered Feb 28 '15 at 08:09

Note this

function FollowMouse()
{
    var len = arguments.length;
    if(len == 0) return;
    //
    for(var i=0; i< len; i++)
    {
        arguments[i].style.top = event.clientY+"px";
        arguments[i].style.left = event.clientX+"px";
    }

};

//---------------------------

html page

<body onmousemove="FollowMouse(d1,d2,d3)">

<p><div id="d1" style="position: absolute;">Follow1</div></p>
<div id="d2" style="position: absolute;"><p>Follow2</p></div>
<div id="d3" style="position: absolute;"><p>Follow3</p></div>


</body>

can call function with any Args

<body onmousemove="FollowMouse(d1,d2)">

or

<body onmousemove="FollowMouse(d1)">

score -2 · Answer 8 · answered Nov 04 '16 at 23:29

-2

var f=d=>
  d.forEach(k=>
    alert(k)
  );
let a=[1,2];
f(a);

fiddle

answered Nov 04 '16 at 23:29

Thielicious

4,122
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javascript: pass an array to a function

8 Answers8

JS Fiddle

Linked