Check if JSON object is defined

Question

I have a JSON object

var values = {"220":{"287":19,"total":19},"":{"240":76,"total":76},"total":95};

and I'm not able to check if values[item]['total'] is defined.

item is variable got from selectbox value, basically I'm trying to make if else statement, I need to check if values[item]['total'] is defined, I have 2 scenarios

item is 220, or another number which goes in "" (json object is generated with php, in this case it has 220 and "", because it doesnt have "color" value, only size, but usally it have correct values)
and in my case item value is the one in {} brackets - for example 287 and 240

This code :

if ( typeof values[item]['total'] === 'undefined' ) {
    console.log('undefined');
}

throws: Uncaught TypeError: Cannot read property 'total' of undefined.

xdazz · Accepted Answer · 2014-04-29 09:11:45Z

2

You could use in to check:

if (item in values && 'total' in values[item]) {
    console.log('defined');
}

answered Apr 29, 2014 at 9:11

xdazz

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Comments

musefan · Accepted Answer · 2014-04-29 09:13:20Z

2

That error will be caused when the value of item does not match any of the properties it will return null, and then you try to access a property of it but you can't because the item is null.

What you should do is check both parts for undefined:

if ( typeof values[item] === 'undefined' || typeof values[item]['total'] === 'undefined') {
    console.log('undefined');
}

Here is a working example

answered Apr 29, 2014 at 9:13

musefan

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1 Comment

mabi Over a year ago

+1 for actually explaining what happens. And providing code based on the OP's.

Murali Murugesan · Accepted Answer · 2014-04-29 09:20:15Z

1

What about using hasOwnProperty()

 if ( typeof values[item]!== 'undefined' && 
      values[item].hasOwnProperty('total')===false ) 
     { 
        console.log('Total undefined'); 
     }

Note: Make sure you are passing a string for item. so it will be compiled as item["220"] and not item[220]. In JavaScript object indexers are accessed by string names

edited Apr 29, 2014 at 9:20

answered Apr 29, 2014 at 9:09

Murali Murugesan

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7 Comments

kriss.andrejevs Over a year ago

this code throws: Uncought TypeError: Cannot read property 'total' of undefined

Murali Murugesan Over a year ago

@kriss.andrejevs make sure you are passing string "220" to a item and not a number 220

mabi Over a year ago

@Murali you pass the if only if the object is not defined. You need to check for !==.

mabi Over a year ago

@Murali Just that your logging output now should say "defined", because that's what you're testing for.

musefan Over a year ago

I think you have kind of missed the problem and suggested a fix that isn't required... although you have addressed the issue after the above comments, it still feels a bit "off course"

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