Loop through JSON array element in Javascript

Question

I have a JSON structure like :

{
    listOfVal: [
        val1,
        val2,
        val3
    ]
    name: "app"
    id: "9209629"
}

I want to check if listOfVal has say val2. val2 can be at any index.

This JSON is part of a response to an API call and I am using:

var data = JSON.parse(responseBody);

to hold the JSON data.

Answer 1

First of all, your JSON isn't valid. You're missing commas and quotes.

{
    "listOfVal": [
        val1,
        val2,
        val3
    ],
    "name": "app",
    "id": "9209629",
    ...
}

once you have data, iterate over it with a for loop. You could use indexOf, but that doesn't work in IE < 9

function isInJSON(data, value){
    for(var i=0; i<data.listOfVal.length; i++){
        if(data.listOfVal[i] === value){
            return true;
        }
    }
    return false;
}

This won't always work if your vals are arrays or objects. If they are, you could run for loops to compare them, or you could use underscore.js: _.isEqual(obj1,obj2).

OP requested using forEach:

var value; //define what you're looking for
data.listOfVal.forEach(function(val,key){
    if(val === value){
        alert('MATCH FOUND: responseBody["' + String(key) + '"] = ' + String(value));
    }
});

Answer 2

If after using JSON.parse you had an object like this:

data = {
    listOfVal: [ 
        val1, 
        val2, 
        val3 
    ],
    name: 'app',
    id: '9209629'
    ...
}

Then you can access listOfVal as if it were any other object, and use indexOf to try to reach val2.

data.listOfVal.indexOf(val2);

This will either return a non-negative integer index where val2 resides in the array, or it will return -1, indicating that val2 does not exist within your array.