Check if value exists in JavaScript object

Question

How would I check in my array of objects, if a specific item exists (in my case MachineId with id 2)?

[{"MachineID":"1","SiteID":"20"},{"MachineID":"2","SiteID":"20"},{"MachineID":"3","SiteID":"20"},{"MachineID":"4","SiteID":"20"}]

I tried this:

if (index instanceof machineIds.MachineID) {
    alert('value is Array!');
} else {
    alert('Not an array');
}

VisioN · Accepted Answer · 2012-11-29 13:51:25Z

13

In cross browser way you may use jQuery.grep() method for it:

var item = $.grep(machineIds, function(item) {
    return item.MachineID == index;
});

if (item.length) {
    alert("value is Array!");
}

answered Nov 29, 2012 at 13:51

VisioN

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Comments

hvgotcodes · Accepted Answer · 2012-11-29 13:57:02Z

5

The simplest to understand solution is to loop over the array, and check each one.

var match;
for (var i = 0; i < yourArray.length; i++) {
   if (yourArray[i].MachineId == 2) 
        match = yourArray[i];
}

Note if there is more than one matching item, this will return the last one. You can also dress this up in a function.

function findByMachineId(ary, value) {
   var match;
    for (var i = 0; i < ary.length; i++) {
       if (ary[i].MachineId == value) 
            match = ary[i];
    }
    return match;
}

edited Nov 29, 2012 at 13:57

answered Nov 29, 2012 at 13:49

hvgotcodes

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2 Comments

Salman Arshad Over a year ago

For the specified data, you should compare to "2" instead of 2.

user1726343 Over a year ago

Or just remove one of those = signs

freedev · Accepted Answer · 2018-04-01 10:23:16Z

4

There are many standard solution, you don't need third party libraries or loop iteratively.

Array some method - since JavaScript 1.6.
Array find method - since ES6
Array findIndex method - since ES6

For example, using some();

var yourArray = [{"MachineID":"1","SiteID":"20"},{"MachineID":"2","SiteID":"20"},{"MachineID":"3","SiteID":"20"},{"MachineID":"4","SiteID":"20"}];

var params = {searchedID: "2", elementFound: null};
var isCorrectMachineID = function(element) {
    if (element.MachineID == this.searchedID);
        return (this.elementFound = element);
    return false;
};

var isFound = yourArray.some(isCorrectMachineID, params)

Array some method accepts two parameters:

callback - Function to test for each element.
thisObject - Object to use as this when executing callback.

Callback function is not coupled with the iteration code and, using thisObject parameter, you can even return to the caller the element found or more data. If such an element is found, some immediately returns true

http://jsfiddle.net/gu8Wq/1/

edited Apr 1, 2018 at 10:23

answered Nov 29, 2012 at 13:56

freedev

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2 Comments

domino_katrino Over a year ago

Tried in Chrome 46. Could not see it in prototype. Is this function really available with all browsers?

freedev Over a year ago

Please have a look here: ecma-international.org/ecma-262/5.1/#sec-15.4.4.17 and here: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

user1726343 · Accepted Answer · 2012-11-29 13:50:24Z

2

You could use this condition:

if (arr.filter(function(v){return this.MachineID == 2;}).length > 0)

answered Nov 29, 2012 at 13:50

user1726343

Comments

ericsoco · Accepted Answer · 2015-12-10 00:57:25Z

2

Old question at this point, but here's an ES6 solution that uses Array.find:

let machine2 = machines.find((machine) => machine.id === '2');
if (machine2) {
    // ...
}

answered Dec 10, 2015 at 0:57

ericsoco

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2 Comments

Zanshin13 Over a year ago

Keep in mind that this does NOT work in all of IE and in half of mobile browsers (as of november 2016): MDN Array.find browser compability

ericsoco Over a year ago

Sure. If you're using ES6, you should be using Babel (or some comparable transpiler.)

Kapilrc · Accepted Answer · 2017-01-02 12:27:06Z

0

var item = [{"MachineID":"1","SiteID":"20"},{"MachineID":"2","SiteID":"20"},{"MachineID":"3","SiteID":"20"},{"MachineID":"4","SiteID":"20"}];

var newItem = item.filter(function(i) {
  return i.MachineID == 2;  //it will return an object where MachineID matches with 2
});

console.log(newItem);  // will print [{"MachineID":"2","SiteID":"20"}]

edited Jan 2, 2017 at 12:27

answered Sep 6, 2016 at 11:48

Kapilrc

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1 Comment

Abhishek Gurjar Over a year ago

please describe working of your code or use self explanatory comments!

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