JavaScript-通过数组中的ID查找对象并进行修改

Question

Please note that the following scenario is for the demonstration purposes only.

Lets assume I have a following array of object:

var obj = [{
    id: 4345345345,
    cat: [{
        id: 1,
        cat: "test1"
    }, {
        id: 2,
        cat: "test2"
    }]
}, {
    id: 3453453421,
    cat: [{
        id: 1,
    }, {
        id: 2,
    }]
}];

My goal is to :

• Find an object within an array with #id 4345345345 , add property selected : true to it
• Then within this object with #id 4345345345 , find cat with #id 2 , add property selected : true to it

---

The below works, however should my array have 1000+ objects it's feels somehow wasteful, can you please suggest any cleaner/clever solution ( possible using underscore)?

 for (var i = 0; i < obj.length; i++) { var parent = obj[i]; if (parent.id === 4345345345) { parent.selected = true; for (var j = 0; j < parent.cat.length; j++) { var sub = parent.cat[j]; if(sub.id === 2) { sub.selected = true; } }; } }; 

Answer 1

Here are a few approaches I can think of

1) change your data structure to use the id's as the key. ie.

4345345345 : cat: { 1 :{ cat: "test1" }, 2 : { cat: "test2" }}

2) Alternatively you can create a temporary lookup table based on the id to directly look the object actual objects; obviously you would only create the look up table one time, or whenever the data changes. This will bring your runtime from O(n) to O(1).