Check if array contains object-only-element in Javascript

Question

I want to check if an array contains only objects. So I created this function:

function arrayContainsObjOnly(arr){
  return arr.join("").replace(/\[object Object\]/g, "") === "";
}

Here is how you would use it:

// return true
arrayContainsObjOnly([
  {"name" : "juan", "age" : 28},
  {"name" : "pedro", "age" : 25}
]);

// return false
arrayContainsObjOnly([
  {"name" : "juan", "age" : 28},
  "name=pedro;age=25"
]);

Is there any cleaner way to do this? Is using the literal "[object Object]" for checking is safe? I also prefer a non-jQuery solution.

If any object in the array overrides .toString() to provide a custom implementation, then this won't work. Also, this would not include Array and Function which are each a type of object (not sure if you want to include them or not). — jfriend00
– jfriend00, Commented Jul 14, 2015 at 3:57
Yes, Array and Function are also excluded. Array must contains literal objects only. — nameless
– nameless, Commented Jul 14, 2015 at 4:05
Here's an actual glitch. If one of the array elements is the literal string "[object Object]", you will get a false positive. So, your method is NOT entirely safe. You will probably have to check that both typeof elem === "object" and that elem.toString() === "[object Object]" for each item to be entirely safe. — jfriend00
– jfriend00, Commented Jul 14, 2015 at 4:10
Ah, you're right!it didn't cross my mind. I might consider your comment. — nameless
– nameless, Commented Jul 14, 2015 at 4:23
Do you intend this to return true if some of the elements are null or undefined or is that an accident of your implementation? — Scott Sauyet
– Scott Sauyet, Commented Jul 14, 2015 at 4:27

Scott Sauyet · Accepted Answer · 2015-07-14 04:30:01Z

1

Conceptually simpler and cleaner, but no less code:

function arrContainsObjOnly(arr) {
  return arr.every(function(el) {
    return Object.prototype.toString.call(el) === '[object Object]';
  });
}

Update

On second thought, this variant would be better, as it would return false on encountering the first non-object:

function arrContainsObjOnly(arr) {
  return !arr.some(function(el) {
    return Object.prototype.toString.call(el) !== '[object Object]';
  });
}

edited Jul 14, 2015 at 4:30

answered Jul 14, 2015 at 4:12

Scott Sauyet

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6 Comments

TaoPR Over a year ago

Please note that for null, undefined elements, this also returns true.

Scott Sauyet Over a year ago

In what environment? Not by spec. See MDN for more info.

TaoPR Over a year ago

Object.prototype.toString.call(null) returns [Object Null] and Object.prototype.toString.call(undefined) returns [Object Undefined].

Scott Sauyet Over a year ago

Close, [object Null]. But that's the point. Why do you say this returns true?

Scott Sauyet Over a year ago

Oh are you saying that the original implementation returned true for those?

|

Scott Sauyet · Accepted Answer · 2015-07-14 04:44:12Z

0

you can use typeof operator

try this one

// CASE 1  :

var arrItem = [
    {"name" : "juan", "age" : 28},
    {"name" : "pedro", "age" : 25},
    "name=pedro,age=25"
]

var boolIsAllContainObject = arrItem.every(function(oneItem,key){ 

    if ((typeof oneItem) === "object") { 
        return true;
    } else {
        return false;
    }
});

console.log(boolIsAllContainObject)   //return false as one element is not object


// CASE 2:

var arrItem = [
    {"name" : "juan", "age" : 28},
    {"name" : "pedro", "age" : 25},
    {"name" : "name=pedro,age=25"}
]

var boolIsAllContainObject = arrItem.every(function(oneItem,key){ 

    if ((typeof oneItem) === "object") { 
        return true;
    } else {
        return false;
    }
});

console.log(boolIsAllContainObject)   //return true allelement are object

edited Jul 14, 2015 at 4:44

Scott Sauyet

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answered Jul 14, 2015 at 4:30

RIYAJ KHAN

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