Checking if object is Array in Parse.com CloudCode

Question

I have this code running on Parse.com CloudCode

queryContact.find().then(function(results) {

    console.log(typeof results); // object

    if (results.constructor !== Array) {

        response.success("Found zero results");

    } else {

        console.log("WHY DID IT GO THROUGH!!!");
    }

}).then...

The find() function normally returns an array, but in my test case it returns 0 results. By logging to console I managed to see that in this case results is a typeof object. I want to proceed with else case only if results is typeof Array. However, my checks fail to capture this, and the code keeps falling through into the else section. None of the checks from this SO question work for me.

possible duplicate of How do you check if a variable is an array in JavaScript? — Dexygen
– Dexygen, Commented Dec 8, 2014 at 12:34
People need to stop answering this question and voting to close it instead — Dexygen
– Dexygen, Commented Dec 8, 2014 at 12:35
Thanks for you diligence George, but I have quoted the same SO question in my question - see bottom. Hence my question here. I was hoping someone here would have experience with Parse's find() function and CloudCode in case they cause some specific behaviours — artooras
– artooras, Commented Dec 8, 2014 at 12:58
Please name your question better then, if it's not generally about "Checking if object is Array" -- that ground has been covered umpteen times before — Dexygen
– Dexygen, Commented Dec 8, 2014 at 13:16
Thanks, I've done that now. I'd appreciate if you removed the suggestion to close it — artooras
– artooras, Commented Dec 8, 2014 at 13:22

artooras · Accepted Answer · 2014-12-08 18:11:58Z

2

I ended up using

if (results.length === 0) {

Somehow this just worked for me.

answered Dec 8, 2014 at 18:11

artooras

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2 Comments

Seth Over a year ago

This is the correct answer for this question, because Parse.com always returns the results array; all you have to do is check its length.

artooras Over a year ago

You may be right, but it's still strange the the returned array does not respond / allow itself to be identified as an Array. The documentation states the the method returns a list, not array. Can this be the difference?

Fizer Khan · Accepted Answer · 2014-12-08 12:33:01Z

1

To check an object is array

 Object.prototype.toString.call(results) === '[object Array]'

answered Dec 8, 2014 at 12:33

Fizer Khan

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7 Comments

artooras Over a year ago

I just tested it, it doesn't work... The else statements is still getting called.

CodingIntrigue Over a year ago

@artooras Here's a question: is results really an array? Or is it an array-like object?

artooras Over a year ago

Good question - the documentation for this function specifies return value as list parse.com/docs/js/symbols/Parse.Query.html#find - I assumed it's an array because that's what I get through Parse's iOS API

CodingIntrigue Over a year ago

Try console.log(Object.prototype.toString.call(results)) and see what that outputs

Fizer Khan Over a year ago

can you tell me what is the output of Object.prototype.toString.call(results)?

|

Amit Prajapati · Accepted Answer · 2014-12-08 12:34:58Z

0

Try this.

 if( Object.prototype.toString.call( someVar ) === '[object Array]' ) {
   alert( 'Array!' );
 }else{
   alert( 'object!' );
 }

answered Dec 8, 2014 at 12:34

Amit Prajapati

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2 Comments

artooras Over a year ago

I just tested it, it doesn't work... The else statements is still getting called.

artooras Over a year ago

Oh, I see. json response is not relevant as it contains a crash error that relates to code happening later in the else case, and which would be prevented if I can stop the else case to run altogether

Andy · Accepted Answer · 2014-12-08 12:35:32Z

0

You can use the following to return the names of JavaScript types:

function toType(x) {
  return ({}).toString.call(x).match(/\s([a-zA-Z]+)/)[1].toLowerCase();
}

toType([]); // array
toType({}); // object

DEMO

answered Dec 8, 2014 at 12:35

Andy

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