JS：如何检查JSON是否包含特定值

Question

Problem

Im working with an array containing multiple events (names & dates) for each event i have to create a point in a SVG.

For each new Date X = X + 5. For each event on the same date Y = Y + 5.

ex:

event 1: date = 1970 X = 10 & Y = 10

event 2: date = 1970 X = 10 & Y = 15

If a point has been drawn i save the position in an JSON. How can i now validate if the position exists in the JSON?

What i tried

    var var events = [{TITLE:"event 1", DATE:"1970"},
                      {TITLE:"event 2", DATE:"1970"},
                      {TITLE:"event 3", DATE:"1970"}];
    var pos_reserved = [];
    var X = 10;
    var Y = 10;
    if (pos_reserved.X != X && pos_reserved.Y != Y){
      Y = 30;
    }
    else if (pos_reserved.X == X && pos_reserved.Y == Y)
    {
      Y = 10;
    }
    else {}
    pos_reserved.push({"X": X,"Y": Y});
    create_point(X, Y);

Answer 1

I am not sure I understand the exact question, but I'll answer to the title.

UnderscoreJS is your best friend!

_.find(events, {DATE: "1970"})
//returns 1st object that matches the year: Object {TITLE: "event 1", DATE: "1970"}

_.filter(events, {DATE: "1970"}).length
//returns the number of objects with that year: 3

Answer 2

I'm not sure I understand your problem fully but I'm gonna try to help you anyway...

In my opinion, one possibility would be to save the data in an object pos_reserved and do something like that

 var pos_reserved = {}; // returns if a position is already reserved or not function isReserved(x, y){ if (!pos_reserved[x]) return false; if (!pos_reserved[x][y]) return false; return true; } // reserve a position function reservePosition(x, y, someInfo){ // only reserve position if it's not already reserved if (!isReserved(x, y)){ // check if you already have points with this x if (!pos_reserved[x]){ // create one if needed pos_reserved[x] = {}; } // save the point pos_reserved[x][y] = someInfo; } else{ // dosomething... } } 

That's it... i think it's the best solution because your JSON object acts like a matrix... So you can easily access every points you saved earlier...

I added 'someValue' to show you that you can save information about this point. You can give a name or whatever you want... It's up to you, but you don't have to use it as weel ;)

Let me know if you have questions ;)

Romain