本地存储无法按预期工作

Question

I built an app that I then built with PhoneGap Build.THe purpose is for it to run a code (starts at var Quotes once per day when the app is loaded).

When debugging why it wasn't working I noticed that in console I was getting back my message "Local storage didn't work". This means that my initial localstorage.getItem which is supposed to make sure the local storage can be read is returning null . So my code never gets executed.

What am I doing wrong?

function onDeviceReady() { //Do something when the app on device is loaded

var localVal = localStorage.getItem('DateOpened'); 

if(localVal  == null){ 

   console.log("LocalStorage did not work...")}

else
{
  var tempd = new Date(); //Get today's date
  var str = tempd.getDay() + tempd.getMonth() + tempd.getFullYear();
  if(localVal.localeCompare(str) == -1) 
              { 
                            var Quotes = [];
                            var ID = [];
                            var Tag = [];
                            var seen = [];

    localStorage.setItem('DateOpened',str);
    console.log("The App Ran, you can get a new fat tomorrow");
    console.log("Todays date:" + str);
  }
 }
}

Answer 1

Initially, there will be no DateOpened item in local storage, so your code will follow the "did not work" branch, because getItem returns null for things that don't exist. That branch never sets anything in DateOpened , so...you'll always follow that branch.

The fix is not to skip over your code setting DateOpened if the device has local storage.

---

There's also an unrelated problem: Your var str = tempd.getDay() + tempd.getMonth() + tempd.getFullYear() does not produce a string, it produces a number formed by adding those values together, since they're all numbers. Your later localeCompare will fail because it's not a string. You also have the fields in the wrong order for a meaningful textual comparison — you need year first, then month, then day.

---

Here's a minimal fix, see comments:

function onDeviceReady() {

    var tempd = new Date();
    // Note that by adding strings in there, we end up with a string instead of adding.
    // Note the order: Year first, then month, then day.
    // Also, since we display it, we put separators in and add 1 to month (since Jan = 0).
    var str = tempd.getFullYear() + "-" + (tempd.getMonth() + 1) + "-" + tempd.getDay();
    var localVal = localStorage.getItem('DateOpened');

    // If we have no stored value, or it's more than a day old by your definition,
    // do your stuff and store the new date
    if (localVal == null || localVal.localeCompare(str) < 0) {
        var Quotes = [];
        var ID = [];
        var Tag = [];
        var seen = [];

        localStorage.setItem('DateOpened', str);
        console.log("The App Ran, you can get a new fat tomorrow");
        console.log("Todays date:" + str);
    }
}

Answer 2

I think this is help full for you.

 function onDeviceReady() { //Do something when the app on device is loaded var localVal = localStorage.getItem('DateOpened'); if (typeof(DateOpened) == "undefined") console.log("LocalStorage did not work...")} else { var tempd = new Date(); //Get today's date var str = tempd.getDay() + tempd.getMonth() + tempd.getFullYear(); var allRecords=JSON.parse(localStorage.getItem("DateOpened")); if(allRecords == -1) { var Quotes = []; var ID = []; var Tag = []; var seen = []; localStorage.setItem('DateOpened',str); console.log("The App Ran, you can get a new fat tomorrow"); console.log("Todays date:" + str); } } }