CODEWITHSUNDEEP
javascriptfunctionarguments
tomsseisums
tomsseisums

Reputation: 13367

Is it safe to operate with and return dynamic arguments?

/*
 * Example function for operating with dynamic arguments
 */
function something(){
    for(var i in arguments){
        arguments[i] = arguments[i] + Math.random() * 25;
    }

    return arguments;
}

There are no errors, have not noticed performance drops, and, the values are changed.

So, is it safe to do such operations on dynamic arguments?

Upvotes: 0

Views: 31

Answers (3)

Bergi
Bergi

Reputation: 664599

Yes, it is safe. Yet, you should beware of the functionality of the arguments object, which differs between Ecmascript implementations and versions. It can be a pseudo-array linked absolutely to the argument variables, but also can be a independent Array instance.

If you know your environment it's OK, elsewhile it's better to code

function something() {
    var l = arguments.length,
        res = new Array(l);
    for(var i=0; i<l; i++) {
        res[i] = arguments[i] + Math.random() * 25;
    }
    return res;
}

Upvotes: 0

Joseph
Joseph

Reputation: 119847

arguments is a "pseudo-array". How would it be different from returning an array? The only downside is that arguments is not an array and therefore, you don't have the array properties and methods you need.

Upvotes: 0

ThiefMaster
ThiefMaster

Reputation: 318518

I would never return it since it's not a real array (see http://javascriptweblog.wordpress.com/2011/01/18/javascripts-arguments-object-and-beyond/ for some information about special behaviour of that object) - so depending on what the calling code does with it, it would fail.

However, you can easily turn it into an array:

var args = Array.prototype.slice.call(arguments);

I would not modify the original object since changes also change the corresponding named arguments in case your function accepts any.

Upvotes: 3

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