[removed] Setting Nested object value by ID

Question

I would like to know what is the best way to update the member of the multilevel object collection in JavaScript

Here is the simplified version of my collection:

this.Steps = [

{ id: 1, text: "test", childSteps: 
  [
    { id: 2, text: "test"},
    { id: 3, text: "test"},
    { id: 4, text: "test", childSteps: 
    [
           { id: 10, text: "test"},
           { id: 11, text: "test"}
    ]}
    },
    { id: 5, text: "test"},
    { id: 6, text: "test"},
    { id: 7, text: "test"},    
    { id: 8, text: "test"},
    { id: 9, text: "test"}
  ]
}
];

The ideal would be to have a function to be called like:

updateObjectByID(11, 'string to be set');

This is easy to be done when we have only 1 level of objects. But when using recursion on multilevel collection its getting much harder.

I'm currently using a function that is parsing the whole collection and building string like :

this.Steps[0].childSteps[3].childSteps[1].text == "string to be set"

and then I do eval() on that string.

I'm sure there might be a much cleaner solution.

Using eval is making my class impossible to compress btw.

Any help would be greatly appreciated.

Thanks in advance

Answer 1

You can build a map of objects by id for direct access:

var map = {};
(function recurse(steps) {
    for (var i=0; i<steps.length; i++) {
        var step = steps[i];
        map[ step.id ] = step;
        if ("childSteps" in step)
            recurse(step.childSteps);
    }
})(this.Steps);

function updateObjectByID(id, string) {
    map[id].text = string;
}

---

A comment on your code: You overcomplified a lot. When the condition if(obj.id == objId) is met, you have your obj reference already!!! Now there is absolutely no need to search for a path to it, build a string from that, and eval it. Just assign directly to its property!

function(steps, objId, value, whatParam, command) {
    if (typeof whatParam == 'undefined')
        whatParam = 'selected';
    $.each(steps, function(index, obj){
        if(obj.id == objId) {
            // removed a lot of unecessary stuff

            // not sure, looks like "value" was evaled sometimes as well
            obj[whatParam] = value;

         } // insert an "else" here if ids are unique
         if (typeof obj.childSteps != 'undefined') {           
             this.setupObjectState(obj.childSteps, objId, value, whatParam, command);
         }
    });
}

Answer 2

You must recursively descend your tree structure searching for the object with the target "id" and replace its text. For example:

function updateObjectByID(obj, id, text) {
  if (!obj) return;
  if (obj.id === id) {
    obj.text = text;
  } else if ((typeof(obj)==='object') && (obj.constructor===Array)) {
    for (var i=0; i<obj.length; i++) {
      updateObjectByID(obj[i], id, text);
    }
  } else if (obj.childSteps) {
    updateObjectByID(obj.childSteps, id, text);
  }
}

updateObjectByID(this.Steps, 11, 'String to be set');

However, this solution can be optimized by tree pruning.

Answer 3

Since you call updateObjectById() with an ID, the ID has to be unique. Why don´t you change your structure like this then:

this.Steps = [
    { id: 1, text: "test" },
    { id: 2, parent: 1, text: "test" },
    { id: 3, parent: 1, text: "test" },
    { id: 4, parent: 1, text: "test" },
    { id: 10, parent: 4, text: "test" },
    { id: 11, parent: 4, text: "test" },
    { id: 5, parent: 1, text: "test"},
    { id: 6, parent: 1, text: "test"},
    { id: 7, parent: 1, text: "test"},    
    { id: 8, parent: 1, text: "test"},
    { id: 9, parent: 1, text: "test"}
]

This way you can easily update your entries like this:

function updateObjectByID(id, text) {
    for(var i = 0; i < this.Steps.length; i++) {
        if(this.Steps[i].id === id) {
            this.Steps[i].text = text;
            break;
        }
    }
}

With the extra attribute parent you can still easily get all the children of an element like this:

function getChildrenByID(id) {
    var array = [];
    for(var i = 0; i < this.Steps.length; i++) {
        if(this.Steps[i].parent === id) {
            array.push(this.Steps[i]);
        }
    }
    return array;
}

Answer 4

function updateObjectByID(id, text) {
    (function setText(steps) {
        for(var i = 0; i < steps.length; i++){
            var step = steps[i];
            if(step.id === id){
                step.text = text;
            }
            if ("childSteps" in step){
                setText(step.childSteps);
            }
        }
    })(this.Steps);
}

Here is demo. http://jsfiddle.net/qDWX8/