Compare object property to variable in localstorage in JavaScript

Question

Is it possible to compare an object property to a variable stored in localstorage using Javascript or Jquery? Here's what I mean...

So I have an object like this:

var persons = [
  {
    "firstName": "Dwight",
    "surName": "Stender",
    "picture": "https://randomuser.me/api/portraits/med/men/99.jpg",
    "id": "1"
  }
]

And I have a variable stored in localstorage (the name is clickId). Now I want to compare the id from the object to that variable in localstorge. I can print them both to the console so I know they work. But when I try to compare them, it suddenly doesn't work anymore (even though the id and the variable contain the same number). This is how I compared the two:

for (i = 0; i < persons.length; i++) {
    if (persons[i].id == localStorage.clickId) {
        document.getElementById("result").innerHTML = "yay"
    } else {
        document.getElementById("result").innerHTML = "nay"
    };
};

Note 1 I have also tried comparing the two with === instead of ==

Note 2 the statements to be executed inside the if...else are just placeholders for the purpose of explanation

What is the problem in this code?

Feras Al Sous
– Feras Al Sous

2017-08-07 13:22:43 +00:00
Commented Aug 7, 2017 at 13:22 — Feras Al Sous
– Feras Al Sous, Commented Aug 7, 2017 at 13:22

Rory McCrossan · Accepted Answer · 2017-08-07 13:29:36Z

5

You need to use localStorage.getItem(key) to retrieve the object you previously stored. Also note that as localStorage can only hold string you'd need to serialise the object before/after saving it. JSON would be ideal for this:

Also note that you can use some() to negate the for loop, and a ternary to simplify the if.

var persons = [{
  "firstName": "Dwight",
  "surName": "Stender",
  "picture": "https://randomuser.me/api/portraits/med/men/99.jpg",
  "id": "1"
}];

var person = JSON.parse(localStorage.getItem('person') || '{}');
document.getElementById("result").innerHTML = persons.some(p => p.id == person.clickId) ? "yay" : 'nay';

localStorage.setItem('person', JSON.stringify({
  clickId: 1
}));

<div id="result"></div>

Working example

edited Aug 7, 2017 at 13:29

answered Aug 7, 2017 at 13:23

Rory McCrossan

338k41 gold badges321 silver badges353 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Kevin Over a year ago

So you can't compare them directly? You have to store the localstorage variable inside another variable?

Rory McCrossan Over a year ago

Yes - the localStorage is a dictionary containing key/value pairs. It does not store information in the manner you're expecting. I updated the answer to give you a more complete example too.

Kevin Over a year ago

Okay I see, just to be clear: if I have "(clickId, 1)" already saved in localstorage, it would be enough for me to change the getItem('person') to getItem('clickId')?

Kevin Over a year ago

How do I replace the "yay" (if it's true) with the property firstName from the persons object? If I print anything other than plain text, it doesn't show... Is that because of the some() method or because of the shortened if...else statement?

Rory McCrossan Over a year ago

Does it need to be the firstName of the found person? If so that's a fundamental logic change

|

Abdessamad139 · Accepted Answer · 2017-08-07 13:29:03Z

0

you can use the inArray method of Jquery without need to use the loop

$.inArray(value, array)

Returns index of value in array. Returns - 1 if the array does not contain the value

answered Aug 7, 2017 at 13:29

Abdessamad139

3256 silver badges17 bronze badges

Collectives™ on Stack Overflow

Compare object property to variable in localstorage in JavaScript

2 Answers 2

6 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

6 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related