Improved way to build nested array of unique values in javascript
- by dualmon
The setup:
I have a nested html table structure that displays hierarchical data, and the individual rows can be hidden or shown by the user. Each row has a dom id that is comprised of the level number plus the primary key for the record type on that level. I have to have both, because each level is from a different database table, so the primary key alone is not unique in the dom.
example: id="level-1-row-216"
I am storing the levels and rows of the visible elements in a cookie, so that when the page reloads the same rows the user had open are can be shown automatically. I don't store the full map of dom ids, because I'm concerned about it getting too verbose, and I want to keep my cookie under 4Kb.
So I convert the dom ids to a compact json object like this, with one property for each level, and a unique array of primary keys under each level:
{
1:[231,432,7656],
2:[234,121],
3:[234,2],
4:[222,423],
5:[222]
}
With this structure stored in a cookie, I feed it to my show function and restore the user's previous disclosure state when the page loads.
The area for improvement:
I'm looking for better option for reducing my map of id selectors down to this compact format. Here is my function:
function getVisibleIds(){
// example dom id: level-1-row-216-sub
var ids = $("tr#[id^=level]:visible").map(function() {
return this.id;
});
var levels = {};
for(var i in ids ) {
var id = ids[i];
if (typeof id == 'string'){
if (id.match(/^level/)){
// here we extract the number for level and row
var level = id.replace(/.*(level-)(\d*)(.*)/, '$2');
var row = id.replace(/.*(row-)(\d*)(.*)/, '$2');
// *** Improvement here? ***
// This works, but it seems klugy. In PHP it's one line (see below):
if(levels.hasOwnProperty(level)){
if($.inArray(parseInt(row, 10) ,levels[level]) == -1){
levels[level].push(parseInt(row, 10));
}
} else {
levels[level] = [parseInt(row, 10)];
}
}
}
}
return levels;
}
If I were doing it in PHP, I'd build the compact array like this, but I can't figure it out in javascript:
foreach($ids as $id) {
if (/* the criteria */){
$level = /* extract it from $id */;
$row = /* extract it from $id */;
$levels[$level][$row];
}
}
