CoffeeScript/JavaScript how do I error if a parameter is not passed?

Question

I thought I was clever by writing code that did this:

someFunction = (arg1, arg2, arg3) ->
  if _.some(arguments, (a) -> a is undefined)
    throw new Error "undefined parameter"

My intent is that if one of the parameters is undefined, throw an error. But I just discovered it doesn't always work: If someone does not pass in a parameter at all, it's not included in the arguments array and therefore it doesn't get checked.

Is there an easy way to throw an error if this function is called like someFunction(1, 2) or someFunction(1) without checking every parameter by hand?

scrblnrd3 · Accepted Answer · 2013-12-24 03:21:54Z

2

Use arguments.length

function doSomething(arg1,arg2,arg3){
    if(arguments.length!=3){
          throw new Error("wrong param count");
    }

}

answered Dec 24, 2013 at 3:21

scrblnrd3

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Comments

thgaskell · Accepted Answer · 2013-12-24 03:21:12Z

1

You could check arguments.length.

function someFunction(arg1, arg2, arg3) {
    if (arguments.length !== 3) throw new Error('undefined parameter');
}

answered Dec 24, 2013 at 3:21

thgaskell

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