context in function in object method

Question

There is piece of code:

var object = {
    findById: function(idNumber) {
        var data = this.childNodes;
        var returnItems = {};

        function callback(node) {
            if (parseInt(node.id) === idNumber)
                returnItems = node;
        };

        function iterator(node, callback) {
            callback(node);
            var nodes = node.childNodes;
            if (nodes === undefined) {
                return;
            };
            for (var i = 0; i < nodes.length; i++) {
                var iterNode = nodes[i];
                iterator(iterNode, callback);
            };
        };

        function bind(func, context) {
            return function() { // (*)
                return func.apply(context, arguments);
            };
        };

        for (var i = data.length - 1; i >= 0; i--) {
            iterator(data[i], callback);
        };

        return returnItems;
    },
}

How to import context in to iterator and callback function? if I put console.log(this) into function iterator() - this will be 'window', but not my object. Also it shouldn't be this.callback this.iterator etc. As I understand it should be like call/apply or bind. How do it?

I think $.proxy is what you are looking for http://stackoverflow.com/questions/4986329/understanding-proxy-in-jquery — Failwyn, Apr 20 '16 at 14:19
[Function.prototype.call](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call) [Function.prototype.apply](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/apply) [Function.prototype.bind](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind) — Pointy, Apr 20 '16 at 14:19

score 0 · Answer 1 · answered Apr 20 '16 at 14:23

0

wherever you use functions do it this way:

functionToCall.apply(this,params); //this or the context you want to have inside

Sample:

function callable() {
   console.log(this);
}
callable(); //logs window
callable.apply({}); //logs {}

answered Apr 20 '16 at 14:23

Mayday

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It is hard to understand...how it will be work at my code? function callback.apply(this,node) { if (parseInt(node.id) === idNumber) returnItems = node; };?? – Triple -B Apr 20 '16 at 14:48
no no no, its not on the definition. its when you call the function. Instead of calling callback(node) you call it: callback.apply(this,node) – Mayday Apr 20 '16 at 15:21

pishpish · Accepted Answer · 2016-04-20T17:18:12.280

Copy a reference to this inside the findById function.

var object = {
  findById: function(idNumber) {
    var data = this.childNodes;
    var returnItems = {};

    // assign this to a variable
    // you can use inside the nested functions
    var that = this;


    function callback(node) {
      if (parseInt(node.id) === idNumber)
        returnItems = node;
    };

    function iterator(node, callback) {
      callback(node);
      var nodes = node.childNodes;
      if (nodes === undefined) {
        return;
      };
      for (var i = 0; i < nodes.length; i++) {
        var iterNode = nodes[i];
        iterator(iterNode, callback);
      };
    };

    function bind(func, context) {
      return function() { // (*)
        return func.apply(context, arguments);
      };
    };


    for (var i = data.length - 1; i >= 0; i--) {
      iterator(data[i], callback);
    };

    return returnItems;
  }
};

Use call or apply.

for (var i = data.length - 1; i >= 0; i--) {
  iterator.call(this, data[i], callback);
};

context in function in object method

2 Answers2