Consider this
var obj = {
process: function run(param) {
return;
}
}
and
runSomething(param);
The situation is that the run function is built elsewhere in the application and contains some additional processing that need to be done to the runSomething response.
is it possible to somehow run obj.run and insert the runSomething into it, so that runSomething can use the param that was passed in as obj.run("something")
Producing the same result as
var obj = {
process: function run(param) {
return runSomething(param);
}
}
you can do this
var obj = {
process: function run(funct, param) {
return funct(param);
}
}
obj.process(runSomething, param);
Related
As I looked through the source code of the find() of mongoose.js, which looks like following:
Query.prototype.find = function(conditions, callback) {
if (typeof conditions === 'function') {
callback = conditions;
conditions = {};
}
conditions = utils.toObject(conditions);
if (mquery.canMerge(conditions)) {
this.merge(conditions);
}
prepareDiscriminatorCriteria(this);
try {
this.cast(this.model);
this._castError = null;
} catch (err) {
this._castError = err;
}
// if we don't have a callback, then just return the query object
if (!callback) {
return Query.base.find.call(this);
}
this._find(callback);
return this;
};
I really don't understand the part
this._find(callback);
what this means? what is the _find in javascript?
Thanks in advance!
Max
what “this._find(callback)” means in Mongoose find() method?
It's a function call. It seems this._find is a supposed to be a function. That function is called and passed the value of callback.
what is the _find in javascript?
Nothing special. It's simply a property with name _find. If you continue looking through the source code, you might discover its definition somewhere.
I have a function that has already been assigned and I would like to append some additional script. When I display the function like:
var func = obj.when_clicked;
alert(func);
The following is displayed:
function object_123(){
object_123_Action();
}
The type is a "function" and the function is executed elsewhere which I cannot change, the code is:
this.when_clicked();
I need to modify the function by appending my own code so it becomes:
function object_123(){
object_123_Action();
my_clicked(obj);
}
Then add that back and over write the when_clicked function.
It does work if I manually add the code like:
obj.when_clicked = function object_123(){object_123_Action();my_clicked(obj);};
However, I do not know what is in the function initially, all I want is to append the:
my_clicked(obj);
I do need the obj to be the actual object of interest which is obj.
You can wrap it:
var f = this.when_clicked;
this.when_clicked = function() {
// Call the original
var rv = f.apply(this, arguments);
// your code here
// Return the original function's return value
return rv;
};
Function#apply calls the original with the specified this flag. arguments is provided by the JavaScript engine: It's a pseudo-array of the arguments your function was called with, so the above just passes all of them on.
Be sure to think about what it means if your function throws an exception, and catch them if you want to suppress them.
If you do this often, you can giev yourself a utility function:
function wrapFunction(f, wrapper) {
return function() {
var rv = f.apply(this, arguments);
wrapper.apply(this, arguments);
return rv;
};
}
Then
this.when_clicked = wrapFunction(this.when_clicked, function() {
// Your code here
});
Or if you want access to the original's return value, potentially changing it:
function wrapFunction(f, wrapper) {
return function() {
var rv = f.apply(this, arguments);
rv = wrapper.call(this, rv, arguments);
return rv;
};
}
Then
this.when_clicked = wrapFunction(this.when_clicked, function(rv, args) {
// Your code here, using `rv` and `args`, which is a pseudo-array
// Potentially update `rv`
return rv;
});
You can store your functions in an array on the object.
Then, loop though the functions in another function and execute them.
var myObj = { 'myfunctions': [ ] };
and to add functions:
myObj.myFunctions.push (function () { /*function code here*/ });
Or if you already have a named function:
myObj.myFunctions.push (nameOfFunction);
And to call all the functions, use this function (don't add this function to myObj)
function executeMyFunctions (myObj) {
for (var i = 0; i < myObj.myFunctions.length; i++) {
myObj.myFunctions[i]();
}
}
Used this answer on another question of #peter. Meant to post here.
I wanted to call the run function that should call the other and action will be done on the base of element_id
NGL = {}
NGL.SceneBuilder = function() {
var yamlFile = 'http://example.com/main.yaml'
var parseYaml = function() {
}
var buildScene = function() {
// other code
simulationStarted(element_id);
}
return {
run: function(element_id) {
parseYaml();
buildScene(element_id);
}
}
}
NGL.SceneBuilder.run('#someid');
You're not executing your factory so NGL.SceneBuilder is a function, not an object having the run property. Call the function :
NGL.SceneBuilder = (function() {
...
})(); // <<===
Note also that you forget to declare the element_id parameter in buildScene but maybe is it just for the question.
function rebuildJSONObject(){
$.getJSON('services.json', function(data) {
//stof start
var input = data;
var output = { myservices: [] };
for (var key in input) {
if (input.hasOwnProperty(key)) {
for (var i = 0, hostsinfo = input[key].hostsinfo; i < hostsinfo.length; i++) {
output.myservices.push({
'nametag': key,
'hostidn': hostsinfo[i]['hostidn'],
'details': hostsinfo[i]['details'],
'currstatus': hostsinfo[i]['currstatus'],
'currstatusclass': hostsinfo[i]['currstatusclass']
});
}
}
}
//stof end
return output;
});
}
//setting it for use later in the script
var serviceJSONObject = rebuildJSONObject();
I know the stuff going on in the function is working properly cause if I apply it to a click event it works charming. However I would rather load the JSON object into memory once and work with it client side there after unless saved. My Problem is however anywhere I call "serviceJSONObject" I get an "undefined" error.
So How am I doing this wrong and how would I define a variable like this early in the game so the rest of the script can use said variable.
The issue is that output is returned before the callback function is called. You should be able to save the value to serviceJSONObject by using a closure:
function rebuildJSONObject(serviceJSONObject){
$.getJSON('services.json', function(data) {
//stof start
var input = data;
// Use the serviceJSONObject that is passed into rebuildJSONObject
serviceJSONObject = { myservices: [] };
for (var key in input) {
if (input.hasOwnProperty(key)) {
for (var i = 0, hostsinfo = input[key].hostsinfo; i < hostsinfo.length; i++) {
serviceJSONObject.myservices.push({
'nametag': key,
'hostidn': hostsinfo[i]['hostidn'],
'details': hostsinfo[i]['details'],
'currstatus': hostsinfo[i]['currstatus'],
'currstatusclass': hostsinfo[i]['currstatusclass']
});
}
}
}
//stof end
});
}
//setting it for use later in the script
var serviceJSONObject;
rebuildJSONObject(serviceJSONObject);
Why not add a cache property to a function that will store the result of the initial output (loaded via ajax) and returning the saved state to any consecutive call.
function rebuildJSONObject(callback) {
var self = this;
if (typeof self.cache !== 'undefined') {
if (typeof callback === 'function') {
callback(self.cache);
}
return;
}
$.getJSON('services.json', function(data) {
//stof start
var input = data,
output = { myservices: [] };
for (var key in input) {
if (input.hasOwnProperty(key)) {
for (var i = 0, hostsinfo = input[key].hostsinfo; i < hostsinfo.length; i++) {
output.myservices.push({
'nametag': key,
'hostidn': hostsinfo[i]['hostidn'],
'details': hostsinfo[i]['details'],
'currstatus': hostsinfo[i]['currstatus'],
'currstatusclass': hostsinfo[i]['currstatusclass']
});
}
}
}
//stof end
self.cache = output;
if (typeof callback === 'function') {
callback(self.cache);
}
return;
});
}
EDIT: For the first time you will need to call this function asynchronously and supply a callback function, for example
rebuildJSONObject(function(output) {
/*
* Process your output here
*/
console.log(output);
});
Each consecutive time you can again use it synchronously:
console.log(rebuildJSONObject.cache);
There are a couple of problems with this.
The call to getJSON is asynchronous so you need to be careful you don't try to use the results before the call has returned your results.
The way it is at the moment, the results will not be returned to serviceJSONObject. The return output statement is setting the return for the anonymous function, not the return value for rebuildJSONObject, so the results will just disappear. If you want the results to be available elsewhwere in code you will either need to store them in a global variable or access them inside the callback.
I am performing a Google local search, and wish to return the lat/long via an object.
The Google search itself works fine.
When inspected (using console.log or alert()) in the object itself, the results field appears to be populated OK.
However, when inspecting the instance of the object (instantiated before running the callback) the result is blank. I'm aware I don't need the accessor function - the end result is the same either way.
Is there something fundamental missing here? Thanks!
function GeoSearch() {
this.results = [];
this.searchComplete = function(localSearch) {
if(localSearch.results[0]) {
var resultLat = localSearch.results[0].lat;
var resultLng = localSearch.results[0].lng;
this.results = localSearch.results[0].lat;
}
}
this.getResults = function() {
return this.results;
}
}
function populateCoords(postcode) {
var localSearch = new google.search.LocalSearch();
var gs = new GeoSearch();
localSearch.setSearchCompleteCallback(gs, gs.searchComplete, [localSearch]);
localSearch.execute(postcode + ", UK");
alert(gs.getResults());
}
When you reference the function gs.searchComplete, you're detaching the method from the object it belongs to. Switch it to function () { gs.searchComplete(); }