I store a lot of values in localStorage for an app and needed a way of converting the "string" back into a number - IF it was a number. The thought being if you force HTML <input type="number"> on your form, then the data going into the form and extracted from the form IS a number, but once stored - its converted to a string. So to repopulate that field later, you must read the localStorage value and convert it back to a number before repopulating the input field - otherwise you start getting a lot of reptitive warnings and sometimes errors because NUMBERS are expected, but localStorage is retrieving strings.
My method: Assuming the value is inputted as a number, then only a number (digits only) will be stored - thus you can assume only numbers will e out (even if they are a string). Knowing only numbers will e back allows for this:
var allVariables = {} ;
var reg = new RegExp(/^\d+$/) ; // this accounts for digits only
for (var x=0; x<localStorage.length;x++) {
var keyValue = localStorage.getItem(localStorage.key(x)) ;
if (reg.text(keyValue)) {
keyValue = parseInt(keyValue) ;
}
allVariables[localStorage.key(x)] = keyValue ;
}
I even expanded on this to account for true/false booleans...can't use 0/1 easily without get confused with a number. Another method I have seen is underscoring the key name to identify the typeof for later conversion:
ie:
key1_str
key2_boo
key3_int
key4_obj
key5_flo
Then identify the "_xxx" to convert that value appropriately.
I am asking to see others approach to this problem or suggestions and remendations on how to improve it. Mine is not perfect...though neither is localStorage...but still looking for improvement.s
I store a lot of values in localStorage for an app and needed a way of converting the "string" back into a number - IF it was a number. The thought being if you force HTML <input type="number"> on your form, then the data going into the form and extracted from the form IS a number, but once stored - its converted to a string. So to repopulate that field later, you must read the localStorage value and convert it back to a number before repopulating the input field - otherwise you start getting a lot of reptitive warnings and sometimes errors because NUMBERS are expected, but localStorage is retrieving strings.
My method: Assuming the value is inputted as a number, then only a number (digits only) will be stored - thus you can assume only numbers will e out (even if they are a string). Knowing only numbers will e back allows for this:
var allVariables = {} ;
var reg = new RegExp(/^\d+$/) ; // this accounts for digits only
for (var x=0; x<localStorage.length;x++) {
var keyValue = localStorage.getItem(localStorage.key(x)) ;
if (reg.text(keyValue)) {
keyValue = parseInt(keyValue) ;
}
allVariables[localStorage.key(x)] = keyValue ;
}
I even expanded on this to account for true/false booleans...can't use 0/1 easily without get confused with a number. Another method I have seen is underscoring the key name to identify the typeof for later conversion:
ie:
key1_str
key2_boo
key3_int
key4_obj
key5_flo
Then identify the "_xxx" to convert that value appropriately.
I am asking to see others approach to this problem or suggestions and remendations on how to improve it. Mine is not perfect...though neither is localStorage...but still looking for improvement.s
Share Improve this question asked Oct 12, 2016 at 17:46 rolingerrolinger 3,0681 gold badge38 silver badges68 bronze badges 5- save it as JSON – Dimava Commented Oct 12, 2016 at 17:50
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Not certain that would work either, because the localStorage has saved the number 12345 as "12345". Importing or saving it as a JSON (without converstion) would still have it as:
"Key" : "12345"versus:"key" : 12345– rolinger Commented Oct 12, 2016 at 17:54 - @rolinger not true...copy my answer to your console and run it – charlietfl Commented Oct 12, 2016 at 17:55
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saved string vill be
'"123"'and number will be'123'. Just parse it back. – Dimava Commented Oct 12, 2016 at 17:57 -
Also look into using
ngStoragemodule. It takes care of all setting and getting and parsing as simple as$localStorage.myData = $scope.data– charlietfl Commented Oct 12, 2016 at 18:09
3 Answers
Reset to default 10suppose you have "keyName" : "12345".
Tricky solution is:
var newInt = +localStorage.getItem('keyName')
this extra + will convert the string to integer.
Instead of storing lots of single keys you might consider storing whole objects to less numbers of storage keys that you stringfiy to json and parse when retrieving. JSON methods will retain type
var obj= {
id:100,
anotherProp:'foo'
}
localStorage.setItem('myObj',JSON.stringify(obj));
var newObj = JSON.parse(localStorage.getItem('myObj'));
console.log(typeof newObj.id)//number
try to convert:
function getProbablyNumberFromLocalStorage(key) {
var val = localStorage.getItem(key);
return (isNan(+val) || val==null) ? val : +val;
}