How to check if a JSON response element is an array?

Question

I am receiving the next JSON response

    {
    "timetables":[
        {"id":87,"content":"B","language":"English","code":"en"},                                                
        {"id":87,"content":"a","language":"Castellano","code":"es"}],
    "id":6,
    "address":"C/Maestro José"
    }

I would like to achieve the next pseudo code functionality

for(var i in json) {            
    if(json[i]  is Array) {
    // Iterate the array and do stuff
    } else {
    // Do another thing
    }
}

Any idea?

James · Accepted Answer · 2009-06-04 16:05:17Z

64

There are other methods but, to my knowledge, this is the most reliable:

function isArray(what) {
    return Object.prototype.toString.call(what) === '[object Array]';
}

So, to apply it to your code:

for(var i in json) {                    
    if(isArray(json[i])) {
    // Iterate the array and do stuff
    } else {
    // Do another thing
    }
}

answered Jun 4, 2009 at 16:05

James

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1 Comment

cimmanon Over a year ago

There is now a native function in JavaScript that will do this (Array.isArray(obj)), though older browsers will still need to rely on this as a polyfill.

sonichy · Accepted Answer · 2017-09-21 16:03:29Z

30

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/isArray

if(Array.isArray(json[i])){
    // true
    ...
}

answered Sep 21, 2017 at 16:03

sonichy

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Comments

Quentin · Accepted Answer · 2009-06-04 16:07:03Z

5

function isArray(ob) {
  return ob.constructor === Array;
}

answered Jun 4, 2009 at 16:07

Quentin

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1 Comment

James Over a year ago

This will work in most situations but it will fail when you're testing an array from a different window/frame since the constructor will be different.

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