How to check if localStorage value is in array?

Question

Based on this answer I should be using $.inArray, therefore I do:

var curPostId = $(".my_post_id").attr("data-id");

if($.inArray(curPostId, lines)) {
  $('#'+localStorage.getItem('saveButton')).attr('disabled', true);
}

If I do: console.log(curPostId); I get 248 which is correct. Then if I do console.log(lines); I get [242, 248]

Lines is defined like this:

var lines = localStorage.getItem("lines") ? JSON.parse(localStorage.getItem("lines")) : [];

But the check if it's in Array doesn't happen as this it's not applied $('#'+localStorage.getItem('saveButton')).attr('disabled', true);

This is how I set daveButton on local storage

$(".save_post").on("click", function() {
  if (counter >= 2) { 
    alert('nope'); 
    return; 
  } else {
    $(this).attr("disabled", "true");
    localStorage.setItem('saveButton', $(this).attr('id'));
    var thisId = $(".my_post_id").attr("data-id");
    lines.push(thisId);
    localStorage.setItem("lines", JSON.stringify(lines));
  }
});

This question is a follow up to my previous question how to keep button state across different pages which has an answer that works but only partly.

Might you simply use the built-in method Array.includes instead? (it's less of a misnomer than inArray, and more closely matches what you're trying to do) — CertainPerformance
– CertainPerformance, Commented Mar 30, 2018 at 6:33
@CertainPerformance actually could you post a link? I only find inArray even when i look for include — rob.m
– rob.m, Commented Mar 30, 2018 at 6:34
That's not a duplicate of what was suggested. This one is more about arrays than checking if a property is in localStorage, which is why I voted for reopening. — acdcjunior
– acdcjunior, Commented Mar 30, 2018 at 6:43

CertainPerformance · Accepted Answer · 2018-03-30 06:41:44Z

2

Just use the Array.includes method instead - it's less confusing, more appropriately matches what you're looking for, and doesn't require jQuery.

if (lines.includes(curPostId)) {
  // ...

Also note that you can simplify your syntax by assigning and getting from localStorage's dot properties directly, for example:

var lines = JSON.parse(localStorage.lines || '[]');
// ... 
localStorage.saveButton = $(this).attr('id');
// ... 
localStorage.lines = JSON.stringify(lines);

answered Mar 30, 2018 at 6:41

CertainPerformance

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10 Comments

CertainPerformance Over a year ago

I just copied that from your line localStorage.setItem('saveButton', $(this).attr('id'));, which you can replace with dot notation if you want to make your code easier to read with less syntax noise.

rob.m Over a year ago

localStorage.saveButton = $(this).attr('id'); shouldn't it be a push? Otherwise each time we land on a page this will be replaced

rob.m Over a year ago

var saveButton = []; then on a click saveButton.push($(this).attr('id')); ?

rob.m Over a year ago

actually the array should be set like i do for lines var saveButton = localStorage.getItem("saveButton") ? JSON.parse(localStorage.getItem("saveButton")) : []; correct?

CertainPerformance Over a year ago

I didn't look at what the code was doing there, I just copied it and converted it into dot notation. But it looks like saveButton is intended to be a string, not an array?

|

Kiran Shinde · Accepted Answer · 2018-03-30 06:42:56Z

1

$.inArray return index of element so what happens is, your element is at '0' th index and if condition will be false if value is 0

So you can use

 if($.inArray(curPostId, lines) !== -1) {

or Use includes method of ES6

if (lines.includes(curPostId)) {

answered Mar 30, 2018 at 6:42

Kiran Shinde

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1 Comment

rob.m Over a year ago

yup, this works, had to accept the other answer as it was firstly suggested on a comment. But the principle is the same and this answer is correct too. Thanks

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