How to remember whether box is checked or unchecke

问题:

Here is the jsfiddle: http://jsfiddle.net/nng6L/7/

So what I want to do is the following:

1. I want to set a value in localstorage, of 1 if box is checked, or 0 if box is unchecked
2. When page is reloaded, if box was checked then it stays checked, having fetched the value from localstorage
3. I want to be able to display either a 1 or a 0 in plain text, having fetched the aforementioned value from localstorage.

Here is my code, but it is not working (when page is reloaded, box is not checked; and null is returned instead of a 1 or a 0):

script.js

    // here is to set item in localstorage when you click the check box.
    vvvvvvv = document.getElementById('xxxx');      
    vvvvvvv.onclick = function() {
        if(document.getElementById('xxxx').checked=true) {
            localStorage.setItem('yyyyyyy', "1");
        } else {
            localStorage.setItem('yyyyyyy', "0");
        }
    }

    // here is to fetch the item stored in local storage, and use that value
    // to check or uncheck the box based on localstorage value.
    zzzzzzz = localStorage.getItem('yyyyyyy');
    if (zzzzzzz === null) {
            localStorage.setItem('yyyyyyy', "0");
            document.getElementById("xxxx").checked=false;
        }
        else {
            if (zzzzzzz === "1") {
                document.getElementById("xxxx").checked=true;
            } else if (zzzzzzz === "0") {
                document.getElementById("xxxx").checked=false;
            }
        }

output.js

    // here is to output the value to the web page so we can know 
    // what value is stored in localstorage.
    wwwwwwww = localStorage.getItem('yyyyyyy');
    document.write(wwwwwwww);

page.html

<!-- here is the check box for which the scripts above are based from -->
<input type="checkbox" id="xxxx">Do you like summer?
<br><br>

<!-- here is where it will display the value from localstorage -->
<script src="output.js">

回答1:

I removed some unnecessary bits of the script and tidied it a little and came up with this...

// here is to set item in localstorage when you click the check box.

vvvvvvv = document.getElementById('xxxx');      

vvvvvvv.onclick = function() {
    if(document.getElementById('xxxx').checked) {
        localStorage.setItem('yyyyyyy', "1");
    } else {
        localStorage.setItem('yyyyyyy', "0");
    }
}

// here is to fetch the item stored in local storage, and use that value
// to check or uncheck the box based on localstorage value.

zzzzzzz = localStorage.getItem('yyyyyyy');

console.log(zzzzzzz);

if (zzzzzzz === "1") {
    document.getElementById("xxxx").checked=true;
} else {
    document.getElementById("xxxx").checked=false;
}

Here's a working jsFiddle...

http://jsfiddle.net/nng6L/5/

Check the checkbox and refresh the page to see it work.

回答2:

There are a couple of syntax errors in your code, which is why it is failing to store the value in localStorage. For example, here is one:

Equality operator in your onclick (== instead of =):

if(document.getElementById('xxxx').checked == true) {

or just:

if(document.getElementById('xxxx').checked) {

Another one:

Extra dangling { before the else as pointed out by dystroy.

Now it is working just fine:

See fiddle: http://jsfiddle.net/nng6L/6/

You did not fix the second! There was an extra { dangling before the else.