I'm creating a JSON object like

tags = {"jon":["beef","pork"],"jane":["chicken","lamb"]};

which was generated using php from an array like

$arr = array(
        'jon' => array('beef', 'pork'),
        'jane' => array('chicken', 'lamb')
       );
$tags = json_encode($arr);

And I want to check if something is in one or the other. None of these seem to work, but something like

if('lamb' in tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

writes NO to the console

if('foo' in tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

also writes NO to the console

so looking at

typeof(tags.jane);

it shows it's an "object" but

console.log(tags);

shows the following:

Object
jane: Array[2]
    0: "chicken"
    1: "lamb"
    length: 2
    __proto__: Array[0]
jon: Array[2]
    0: "beef"
    1: "pork"
    length: 2
    __proto__: Array[0]
__proto__: Object

so i thought maybe tags.jane may actually be an array and tried

if($.inArray('lamb', tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

which writes YES to the console but

if($.inArray('foo', tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

also writes YES to the console.

Am I incorrectly building the JSON Object? Not targeting the value(s) properly? Any advice is greatly appreciated. If this would be easier as an array instead of an object, I have full control to change it. I'm just a bit stumped at how I should treat this.

I'm creating a JSON object like

tags = {"jon":["beef","pork"],"jane":["chicken","lamb"]};

which was generated using php from an array like

$arr = array(
        'jon' => array('beef', 'pork'),
        'jane' => array('chicken', 'lamb')
       );
$tags = json_encode($arr);

And I want to check if something is in one or the other. None of these seem to work, but something like

if('lamb' in tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

writes NO to the console

if('foo' in tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

also writes NO to the console

so looking at

typeof(tags.jane);

it shows it's an "object" but

console.log(tags);

shows the following:

Object
jane: Array[2]
    0: "chicken"
    1: "lamb"
    length: 2
    __proto__: Array[0]
jon: Array[2]
    0: "beef"
    1: "pork"
    length: 2
    __proto__: Array[0]
__proto__: Object

so i thought maybe tags.jane may actually be an array and tried

if($.inArray('lamb', tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

which writes YES to the console but

if($.inArray('foo', tags.jane)) {
    console.log('YES');
} else {
    console.log('NO');
}

also writes YES to the console.

Am I incorrectly building the JSON Object? Not targeting the value(s) properly? Any advice is greatly appreciated. If this would be easier as an array instead of an object, I have full control to change it. I'm just a bit stumped at how I should treat this.

• javascript
• jquery
• json

• use JSON.parse( jsonString ) to convert the server response to a javascript object. – Larry Battle Commented Apr 6, 2012 at 18:34
• 2 +1 for a thorough demonstration of what you tried. – user1106925 Commented Apr 6, 2012 at 18:41
• sorry i didn't mention i was parsing the JSON in the js, but either way Sergio (and others) gave me what I needed. Thanks all! Out of curiosity, why are tags.jane and tags.jon arrays instead of "nested objects" is that just not possible in JSON? when i started this i was thinking i'd do a check like if(tags.jane.chicken) expecting it to return true or false if the property existed. i obviously need to do some reading on JSON objects. :P Thanks again to all those that chimed in. – ocergynohtna Commented Apr 6, 2012 at 18:49
• 1 @amnotiam: if only there were more questions like this :) – Sergio Tulentsev Commented Apr 6, 2012 at 19:17
• 1 @SergioTulentsev: Agreed. @@ocergynohtna: JSON has 2 data structures. One is an ordered list (an Array) where the keys are excluded in the markup, because they're implicitly 0-based indices. The other is an collection of key/value pairs, where the keys can be any string value. To get the tags.jane.chicken behavior, you'd need to use chicken as a key, and choose true (or another truthy value) as the value, and use the {} syntax for object notation. {"jon":{"beef":true,"pork":true},"jane":{"chicken":true,"lamb":true}} – user1106925 Commented Apr 6, 2012 at 19:26

5 Answers 5

jQuery.inArray returns -1 when element is not found. That's true value from the POV of Javascript. Try this:

if($.inArray('foo', tags.jane) != -1) {

Your second set of answers are the way you should go. However, $.inArray returns an index, not a boolean. Any non-zero integer is true, which means when foo is not found, it returns -1 which evaluates to true and prints YES.

Similarly, $.inArray('chicken', tags.jane) would return 0 and cast to false, which is also not the answer you want.

Instead, use $.inArray('foo', tags.jane) !== -1 as your condition.

tags.name will give you the array for that person. So $.inArray("chicken",tags.jane) would see if "chicken" is in jane's tags array. If it's not, you'd get -1, otherwise you'd it's position in the array (using your example, this would return zero, the first array element).

You're using the keyword in for the wrong reason. The statement ( prop 'in' obj ) checks to see if the object(associated array) has a property with the value of prop. Since you're using the 'in' keyword on an array, then false is going to be returned because tags.jane is an array with indexes and not an associated array with properties.

If you want to know was values are in the array then loop through and pare. If you want to use the 'in' keyword then convert your array to an object like so.

    tags = {};
    // old code
    tags.jane = ['lamb', 'food']; 
console.log(('lamb' in tags.jane) === false )
    // new code
    tags.jane = {
       'lamb':1,
        'food':1
    }
console.log(('lamb' in tags.jane) === true )

https://developer.mozilla/en/JavaScript/Reference/Statements/for...in

you can not use

if('foo' in tags.jane))

it should be used as

if (1 in tags.jane)

if you want to check 'foo' is in tags.jane, try this

var inIt = (function() {
    var inIt = false;
    tags.jane.forEach(function(item) {
        inIt = inIt || 'foo' == item;
    });
    return inIt;
})();