HTML5 localStorage: Big JSON, specific value as co

问题:

Given a large JSON table in localStorage and a given key, how to access an associated value, and use it as a condition to CSS ? 

Given the following JSON:

var data = [ 
{ 'myKey': 'A', 'status': 0 },
{ 'myKey': 'B', 'status': 1 },
{ 'myKey': 'C', 'status': 1 },
{ 'myKey': 'D', 'status': 1 }
];

the following html to stylize:

<p id="A">AA</p>
<p id="B">BB</p>
<p id="C">CC</p>
<p id="D">DD</p>

and the following css :

.status1 { color: green; }
.status0 { color: red; }

It's one of the basic principle behind "click to favorite/ favorite list / favorite star".

回答1:

Working example on fiddle, JQuery

0. Trick for Apps!: JSON & localStorage

/* To store JSON in localStorage, you compress it as string */
    localStorage["results"] = JSON.stringify(data); // or lS.restults

/* Whenever you want to work on it, need to uncompress the JSON */
    var data = JSON.parse(localStorage["results"]);

1. Create the meta functions: getJsonVal()

//META.Fn: pullVal
function getJsonVal(json, itemId) {
    for (var i in json) {
        if (json[i].myKey == itemId) {
            return json[i]; 
        }
    }
}

2. Function checking the JSON value before to inject CSS class accordingly

//META.Fn: loadSwitch [check localStorage & set CSS
function loadSwitchCSS($set, i) {
    setTimeout(function () {
        var myID = $set.eq(i).attr('id'); // a. Get key [my case: from the html ID]
        alert("look at:"+ myID);
        var val = getJsonVal(data, myID).status;
        // alert(data);
        if (val == 1) { // c. CSS remove-add: so if...else... CSS
            $set.eq(i).removeClass().addClass('status1');
        } else {
            $set.eq(i).removeClass().addClass('status0')
        }
        if (i < $set.length - 1) {
            loadSwitchCSS($set, i + 1);
        }
    }, 100);
}

3. Fire the function on load:

loadSwitchCSS($('p'), 0);