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How can I check if an item is set in localStorage ? Currently I am using

if (!(localStorage.getItem("infiniteScrollEnabled") == true || localStorage.getItem("infiniteScrollEnabled") == false)) {
    // init variable/set default variable for item
    localStorage.setItem("infiniteScrollEnabled", true);
The getItem method in the WebStorage specification, explicitly returns null if the item does not exist:
  
... If the given key does not exist in the list associated with the object then this method must return null. ...
So, you can:
if (localStorage.getItem("infiniteScrollEnabled") === null) {
  //...
See this related question:
Storing Objects in HTML5 localStorage
                Could you add your own method to localStorage to encapsulate this little test? E.g. localStorage.hasItem("infiniteScrollEnabled")?
– Paul D. Waite
                Jul 17, 2010 at 1:10
                @Paul: Yes, you could even augment the Storage.prototype object, but as a rule of thumb I always recommend to not modify objects you don't own, specially host objects.
– Christian C. Salvadó
                Jul 17, 2010 at 18:10
                ooh yeah, good points in there. Coming from a CSS background, the idea that I can fix browser issues myself is exciting, but I can see how mucking around with the browser’s objects could get confusing.
– Paul D. Waite
                Jul 19, 2010 at 9:38
                Thanks! However, since the question tries to set a value in Storage to true and checks if it's true, it may be a good idea to mention that keys and values can only be strings, and anything you pass as a value is implicitly converted to a string.
– Timothy Zorn
                Mar 8, 2017 at 15:53
                It should be the accepted answer. The accepted one will consider a stored "null" value as not set, which is wrong.
– Flavien Volken
                Jun 5, 2018 at 9:53
                @FlavienVolken You can not have a stored null value though. You can have "null", but the code there will not misbehave on it, while this one will fail on length key.
– Kaiido
                Sep 4, 2018 at 2:34
                @Kaiido you are right, I had this behaviour because I was directly parsing the stored data and as JSON.parse("null") === JSON.parse(null) I had a collision.
– Flavien Volken
                Sep 4, 2018 at 14:32
                Got the following ESLint error: "Do not access Object.prototype method 'hasOwnProperty' from target object.eslint(no-prototype-builtins)"
– rfdc
                Jan 3, 2019 at 11:32
                This won't work if foo is not set on page load and you want to do something with foo. I think that is what the questioner was getting at, you want to check if the key foo exists, not if foo has a value. I have this situation, where a click event triggers .setitem with logic based around getItem,but it won't work until I setItem, and I can't setItem until I know foo's state (value1 or value2). In other words, check foo exits then set it to value1 if it does not without accidentally overwriting value2.
– Rin and Len
                Feb 14, 2020 at 11:56
The shortest way is to use default value, if key is not in storage:
var sValue = localStorage['my.token'] || ''; /* for strings */
var iValue = localStorage['my.token'] || 0; /* for integers */
there are couple of methods to check i am adding them here
Method 1
if("infiniteScrollEnabled" in localStorage){
     console.log("Item exists in localstorage");
}else{
    console.log("Item does not exist in localstoarge";
Method 2
if(localStorage.getItem("infiniteScrollEnabled") === null){
    console.log("Item does not exist in localstoarge";
}else{
   console.log("Item exists in localstorage");
Method 3
if(typeof localStorage["cart"] === "undefined"){
    console.log("Item does not exist in localstoarge";
}else{
   console.log("Item exists in localstorage");
Method 4
if(localStorage.hasOwnProperty("infiniteScrollEnabled")){
     console.log("Item exists in localstorage");
 }else{
    console.log("Item does not exist in localstoarge";
                JavaScript returns the first non-null or positive value   Examples:  [ null || "abc" ] will return "abc" [ 2 || 5 ] will return 2 [ 0 || 5 ] will return 5 [ 1 || 5 ] will return 1 etc. Hence the above code works.
– Deepak Thomas
                May 21, 2018 at 14:19
You can also try this if you want to check for undefined:
if (localStorage.user === undefined) {
    localStorage.user = "username";
getItem is a method which returns null if value is not found.
How can one test existence of an item in localStorage?
this method works in internet explorer.
<script>
        localStorage.getItem("username");
    }catch(e){
        alert("we are in catch "+e.print);
</script>
Best and Safest way i can suggest is this, 
if(Object.prototype.hasOwnProperty.call(localStorage, 'infiniteScrollEnabled')){
    // init variable/set default variable for item
    localStorage.setItem("infiniteScrollEnabled", true);
This passes through ESLint's no-prototype-builtins rule.
You should check for the type of the item in the localStorage
if(localStorage.token !== null) {
   // this will only work if the token is set in the localStorage
if(typeof localStorage.token !== 'undefined') {
  // do something with token
if(typeof localStorage.token === 'undefined') {
  // token doesn't exist in the localStorage, maybe set it?
I've used in my project and works perfectly for me 
var returnObjName= JSON.parse(localStorage.getItem('ObjName'));
if(returnObjName && Object.keys(returnObjName).length > 0){
   //Exist data in local storage
}else{
  //Non Exist data block
I'm late to this party, but checking localStorage for the existence of keys (or the existence of key values) is easily done with localDataStorage, a handy utility wrapper I created.
After instantiating the wrapper with something like
myLDS = localDataStorage( 'segmentedStorageHere' );
you can set keys
myLDS.set( 'infiniteScrollEnabled', true );
in a straightforward manner. Note that this example is actually passing a boolean value to the store, where it can be retrieved with
let scrollingState = myLDS.get( 'infiniteScrollEnabled' );
and scrollingState will contain the boolean value returned. The wrapper keeps track of the native JavaScript data type for you, seamlessly (Array, Boolean, Date, Number, Object, etc.) No more JSON stringifying/parsing in your code.
Now when we need to know if a key is in the store, we can check it like this
if( myLDS.haskey( 'infiniteScrollEnabled' ) ) {
    console.log( "It's been set!" ); 
} else {
    console.log( "The key is not set." ); 
You can also check whether a particular value is present. For example
myLDS.set( 'myNumber', 1234.5678 );
console.log( myLDS.hasval( 1234.5678 ) );    --> true
As @Christian C. Salvadó has mentioned above you can do
if (xxx === null){}
but null is also a falsy value, like so:
if (null){
console.log ("hello");
which does not print "hello".
I always check if localStorage or sessionStorage is set by checking the length of them
if (sessionStorage.length > 0) {
  console.log("exists")
} else {
  console.log("not exists")
                Do or do not. There is no "try". A good answer will always have an explanation of what was done and why it was done in such a manner, not only for the OP but for future visitors to SO.
– Jay Blanchard
                Apr 27, 2020 at 15:33
        
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