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.

Billy Moon · Accepted Answer · 2012-10-27 01:15:39Z

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, 2012 at 1:15

Billy Moon

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6 Comments

roberkules Over a year ago

or my_array.push("a", "b", "c")

Billy Moon Over a year ago

@roberkules: I like that one, I think you deserve a prize for that.

Billy Moon Over a year ago

@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).

roberkules Over a year ago

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.

Billy Moon Over a year ago

let us continue this discussion in chat

|

jcolebrand · Accepted Answer · 2012-10-27 01:14:59Z

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, 2012 at 1:14

jcolebrand

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3 Comments

David G Over a year ago

Not in JS you don't. Functions are hoisted.

jcolebrand Over a year ago

Good point David, hoisting. Forgot that. Updated to make it about a good business practice.

Billy Moon Over a year ago

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) }

Community · Accepted Answer · 2017-05-23 12:34:45Z

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, 2017 at 12:34

CommunityBot

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answered Oct 27, 2012 at 1:18

Andreas Louv

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Comments

codingbiz · Accepted Answer · 2012-10-27 01:22:59Z

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, 2012 at 1:22

answered Oct 27, 2012 at 1:17

codingbiz

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Comments

roberkules · Accepted Answer · 2012-10-27 01:23:41Z

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, 2012 at 1:23

answered Oct 27, 2012 at 1:17

roberkules

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2 Comments

Andreas Louv Over a year ago

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?

roberkules Over a year ago

okay, so it's a popular way (I see it in many js libraries) to define arrays of strings.

Fauzan DP · Accepted Answer · 2022-11-09 02:35:16Z

0

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


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

print_array(my_array);

answered Nov 9, 2022 at 2:35

Fauzan DP

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1 Comment

Rohit Gupta Over a year ago

Its always best if you explain the answer.

ali.b.y · Accepted Answer · 2015-02-28 08:09:20Z

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)">

Thielicious · Accepted Answer · 2016-11-04 23:29:35Z

-2

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

fiddle

answered Nov 4, 2016 at 23:29

Thielicious

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