Using eval() in Javascript to unpack the array

Question

I have an array that I need to unpack.

So, from something like

var params = new Array();
params.push("var1");
params.push("var2");

I need to have something like

"var1", "var2".

I tried using eval, but eval() gives me something like var1, var2...i don't want to insert quotes myself as the vars passed can be integers, or other types. I need to pass this to a function, so that's why i can't just traverse the array and shove it into a string.

What is the preferred solution here?

I doubt you can get JavaScript to add the " itself, unless maybe you use JSON.stringify(). " are just the string delimiters and do not belong to the string value. — Dormilich
– Dormilich, Commented May 25, 2010 at 22:06
that's the thing, is that i would like to pass the VALUES of the vars...they may not always be strings either. I am wondering if it's possible at all. — sarsnake
– sarsnake, Commented May 25, 2010 at 22:16
I'm trying to come up with a general solution, so at the point of passing I won't know how many parameters the function will accept. Hence, I shove them into the array. Then, I need to unpack and pass them. So the variables shoved into the array may all be different types:strings, ints, other arrays. When unpacking, I want to be able to do something like: DoSomething(param1, param2, param3) where param1 .. param3 come from the array. I posted here: stackoverflow.com/questions/2836037/… got no real answers — sarsnake
– sarsnake, Commented May 25, 2010 at 22:27

Sean Kinsey · Accepted Answer · 2010-05-25 23:03:06Z

7

If you have an array of values that you want to pass to a function filling the formal parameters then you can use the apply method of the Function prototype.

var arr = [1, 2, "three"];

function myFunc(a, b, c) {
   // a = 1, b = 2, c = "three"
   ...
}

myFunc.apply(this, arr);

By the way, the this parameter in the last statement can be set to any object to set the value of this inside myFunc

edited May 25, 2010 at 23:03

answered May 25, 2010 at 22:44

Sean Kinsey

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2 Comments

sarsnake Over a year ago

thanks, I never knew of apply's existence. However, what's the purpose of this here? I am not quite clear regarding "this". Do I need it?

Sean Kinsey Over a year ago

You need something there, if you are uncertain use this to keep the current context, or pass null to use the global context. As I said, the first parameter controls what this inside the function refers to.

BrunoLM · Accepted Answer · 2010-05-25 22:50:12Z

0

This generates the output you want

var params = new Array();
params.push("var1");
params.push("var2");

var s = "\"" + params.join("\",\"") + "\"";

answered May 25, 2010 at 22:50

BrunoLM

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