Question

I’m using PHP to fetch “tasks” from my database and encoding it as JSON. When I transfer the data over to javascript, I end up with something like this:

Array {
   [0] => Task {
      id: 2,
      name: 'Random Task',
      completed: 0
   }
   [1] => Task {
      id: 8,
      name: 'Another task',
      completed: 1
   }
}

etc.

I guess my real question is, what’s the most efficient way to find the task by its id? Iterating through the array and checking each object seems like it might not be the most efficient? Is there any other way to do this?

Answer 1

The thing about Javascript objects is that they are essential maps. You can access properties through using both dot notation (“object.property”) and also index notation (“object[“property”]). You can also enumerate through its properties, either using a for (i…) or for (in…)

for (var i = 0; i < arrayObj.length; i++) { ... }

for (var prop in arrayObj) { ... }

What I have been doing recently is building some Linq-esque extensions to the array object:

Array.prototype.Where = function(predicate) {
    Throw.IfArgumentNull(predicate, "predicate");
    Throw.IfNotAFunction(predicate, "predicate");

    var results = new Array();
    for (var i = 0; i < this.length; i++) {
        var item = this[i];
        if (predicate(item))
            results.push(item);
    }

    return results;
};

Ignoring my custom Throw type, it basically allows you do to something like:

var item = arrayObj.Where(function(i) { return (i.id == 8); }).FirstOrDefault();

I’ll publish it all at some point if you are interested?