Monday, April 30, 2018

javascript - Check if localStorage is available



I know there has been many questions about checking for localStorage but what if someone manually shuts it off in their browser? Here's the code I'm using to check:



localStorage.setItem('mod', 'mod');
if (localStorage.getItem('mod') != null){
alert ('yes');
localStorage.removeItem('mod');
} else {
alert ('no');
}


Simple function and it works. But if I go into my Chrome settings and choose the option "Don't Save Data" (I don't remember exactly what it's called), when I try to run this function I get nothing but Uncaught Error: SecurityError: DOM Exception 18. So is there a way to check if the person has it turned off completely?



UPDATE: This is the second function I tried and I still get no response (alert).



try {
localStorage.setItem('name', 'Hello World!');
} catch (e) {
if (e == QUOTA_EXCEEDED_ERR) {
alert('Quota exceeded!');
}
}

Answer



Use modernizr's approach (you might want to change my function name to something better):



function lsTest(){
var test = 'test';
try {
localStorage.setItem(test, test);
localStorage.removeItem(test);
return true;
} catch(e) {
return false;
}
}

if(lsTest() === true){
// available
}else{
// unavailable
}


It's not as concise as other methods but that's because it's designed to maximise compatibility.



The original source: https://github.com/Modernizr/Modernizr/blob/master/feature-detects/storage/localstorage.js



Working example: http://jsfiddle.net/6sm54/2/


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