I have written some javascript that I would to encapsulate in a closure so I can use it elsewhere. I would like do do this similar to the way jQuery has done it. I would like to be able to pass in an id to my closure and invoke some functions on it, while setting some options. Similar to this:
<script type="text/javascript">
_snr("#canvas").draw({
imageSrc : someImage.png
});
</script>
I have read a lot of different posts on how to use a closure to do this but am still struggling with the concept. Here is where I left off:
_snr = {};
(function (_snr) {
function merge(root){
for ( var i = 1; i < arguments.length; i++ )
for ( var key in arguments[i] )
root[key] = arguments[i][key];
return root;
}
_snr.draw = function (options) {
var defaults = {
canvasId : 'canvas',
imageSrc : 'images/someimage.png'
}
var options = merge(defaults, options)
return this.each(function() {
//More functions here
});
};
_snr.erase = function () {};
})(_snr);
When ever I try to call the draw function like the first code section above, I get the following error, '_snr is not a function'. Where am I going wrong here?
EDIT
Here is what I ended up doing:
function _snr(id) {
// About object is returned if there is no 'id' parameter
var about = {
Version: 0.2,
Author: "ferics2",
Created: "Summer 2011",
Updated: "3 September 2012"
};
if (id) {
if (window === this) {
return new _snr(id);
}
this.e = document.getElementById(id);
return this;
} else {
// No 'id' parameter was given, return the 'about' object
return about;
}
};
_snr.prototype = (function(){
var merge = function(root) {
for ( var i = 1; i < arguments.length; i++) {
for ( var key in arguments[i] ) {
root[key] = arguments[i][key];
}
}
return root;
};
return {
draw: function(options) {
var defaults = {
canvasId : 'canvas',
imageSrc : 'images/someimage.png'
};
options = merge(defaults, options);
return this;
},
erase: function() {
return this;
}
};
})();
I can now call:
<script type="text/javascript">
_snr("#canvas").draw({
imageSrc : someImage.png
});
</script>
Because you declared _snr as an object and not a function. Functions can have properties and methods, so there's various ways to achieve what you want, for example one of them would be say...
_snr = function(tag) {
this.tag = tag;
}
_snr.foo = function() {
//Code goes here
}
You can also pass the outer context into a closure to hide your variables from accidentally polluting the global namespace, so like...
(function(global) {
var _snr = function(tag) {
this.tag = tag;
}
_snr.foo = function() {
//Code goes here
}
//export the function to the window context:
global._snr = _snr;
})(window);
window._snr('#tag').foo('wat');
Happy coding.
Because your _snr is an object, not a function. You have to call it like this:
_snr.draw({
canvasId: '#canvas',
imageSrc: 'someImage.png'
});
When you do _snr('#canvas') that is a function call which is why you're getting that error. _snr is an object with some methods attached to it such as draw() and erase(). The reason jQuery is able to pass arguments into the $ is because they return the $ as a function object which is why we're able to pass it various selectors as arguments.
You are going wrong at the first line _snr = {}
It needs to be
_snr = function(){
selector = arguments[0]||false;
//snr init on dom object code
return _snrChild;
}
Im on a mobile phone but when im on a pc I will maybe fix the whole code c:
Here you have a snr object and that has erase and draw methods. What you intend to do is to write a _snr function which will get an id and return a wrapper object. That returned object should have erase and draw methods. so you can do
var returnedObject = _snr("my_id");
returnedObject.draw("image.png");
Related
Im struggling to find a way to get the properties Override & Justification available outside of the function. The code is:
self.CasOverridesViewModel = ko.observable(self.CasOverridesViewModel);
var hasOverrides = typeof self.CasOverridesViewModel === typeof(Function);
if (hasOverrides) {
self.setupOverrides = function() {
var extendViewModel = function(obj, extend) {
for (var property in obj) {
if (obj.hasOwnProperty(property)) {
extend(obj[property]);
}
}
};
extendViewModel(self.CasOverridesViewModel(), function(item) {
item.isOverrideFilledIn = ko.computed( function() {
var result = false;
if (!!item.Override()) {
result = true;
}
return result;
});
if (item) {
item.isJustificationMissing = ko.computed(function() {
var override = item.Override();
var result = false;
if (!!override) {
result = !item.hasAtleastNineWords();
}
return result;
});
item.hasAtleastNineWords = ko.computed(function() {
var justification = item.Justification(),
moreThanNineWords = false;
if (justification != null) {
moreThanNineWords = justification.trim().split(/\s+/).length > 9;
}
return moreThanNineWords;
});
item.isValid = ko.computed(function() {
return (!item.isJustificationMissing());
});
}
});
}();
}
I've tried it by setting up a global variable like:
var item;
or
var obj;
if(hasOverrides) {...
So the thing that gets me the most that im not able to grasp how the connection is made
between the underlying model CasOverridesviewModel. As i assumed that self.CasOverridesViewModel.Override() would be able to fetch the data that is written on the screen.
Another try i did was var override = ko.observable(self.CasOverridesViewModel.Override()), which led to js typeError as you cannot read from an undefined object.
So if anyone is able to give me some guidance on how to get the fields from an input field available outside of this function. It would be deeply appreciated.
If I need to clarify some aspects do not hesitate to ask.
The upmost gratitude!
not sure how far outside you wanted to go with your variable but if you just define your global var at root level but only add to it at the moment your inner variable gets a value, you won't get the error of setting undefined.
var root = {
override: ko.observable()
};
root.override.subscribe((val) => console.log(val));
var ViewModel = function () {
var self = this;
self.override = ko.observable();
self.override.subscribe((val) => root.override(val));
self.load = function () {
self.override(true);
};
self.load();
};
ko.applyBindings(new ViewModel());
<script src="https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.2/knockout-min.js"></script>
I have a web page. In my web page I'm referencing some JavaScript I've written in a file called "spacer.js". spacer.js is more complicated, but the general setup is like this:
function spacer() {
// do stuff
console.log(spacer.options);
}
spacer.initialize = function(options) {
spacer.options = options;
};
Then, in my web page, I have:
<script type="text/javascript" src="./spacer.js"></script>
<script type="text/javascript">
spacer.initialize({ id:1 });
window.onresize = spacer();
</script>
When I load my web page, I get an error that says:
Uncaught TypeError: spacer.initialize is not a function.
I don't understand. What am I doing wrong.
function spacer() {
// do stuff
console.log(spacer.options);
}
spacer.initialize = function(options) { // needed an assignment operator and function keyword
spacer.options = options;
}
To create a method you need to use the function keyword.
To the browser, this
spacer.initialize(options) {
spacer.options = options;
}
is interpreted like this
spacer.initialize(options); // method evocation
{spacer.options = options;}; // anonymous object
Change the way it is defined
//from
spacer.initialize(options) {
spacer.options = options;
}
//to
spacer.initialize = function(options) {
spacer.options = options;
}
In your JS remove the () from window.resize call
spacer.initialize({ id:1 });
window.onresize = spacer;
As an aside it looks like you're trying to do one of two things and sitting uncomfortably in the middle. I'd personally go for 1) in this instance, but probably best to stick with one or the other.
1) Creating an object with methods
var spacer = {};
spacer.initialize = function (options) {
this.options = options;
}
spacer.getOptions = function () {
return this.options;
}
spacer.initialize({ name: 'spacer' });
spacer.getOptions(); // { name: spacer });
DEMO
2) Using a constructor function to build an space object instance:
function Spacer() {}
Spacer.prototype.initialize = function (options) {
this.options = options;
return this;
}
Spacer.prototype.getOptions = function () {
return this.options;
}
var spacer = new Spacer().initialize({ name: 'spacer' });
spacer.getOptions(); // { name: 'spacer' }
DEMO
Trying to define a couple of functions like so:
user = (function() {
var friends_list = (function() {
$.get('/ajax/user/friends_list', function(data) {
......
So I can later on call them when need it like so user.friends_list() but for now, the only thing I get is this following error:
TypeError: Object function () {
var friends_list = (function() {
$.get(....
I just don't know where else to look, any suggestions?
You need to create user as an object, in your case the friends_list is a closure method, it will be availble outside the function
user = {
friends_list : function(){
....
}
}
make a user object and not function
var user = {
friends_list : function(){
$.get('/ajax/user/friends_list', function(data) {
......
}
}
and call it like.. user.friends_list()
fiddle here
You're using a closure here, so friend_list is invisible on the outside of user.
If you want to use closures, to hide some variables, to best way to export friend_list would be:
(function(){
var somePrivateVariable;
window.user = {};
window.user.friend_list = function() {
// make use of somePrivateVariable...
};
})();
user = function() {
this.friends_list = function() {
$.get('/ajax/user/friends_list', function(data) {
......
});
};
return this;
};
Above should also work.
reference http://www.w3schools.com/js/js_objects.asp
You can check out this link
Here is the code:
var global = {};
global.sayHello = function (x){
//do your code here
console.log('Hello ' + x );
};
global.sayHello('Kevin');
user = new function(){
var private_variable;
function private_method(){}
this.global_variable = '';
this.global_method = function(){};
}
I cannot find an proper example for the love of my life on how to do this or even if this is possible. Based on my pieced together understanding from fragments of exmaples, I have come up with the following structure
var t = function()
{
this.nestedOne = function()
{
this.nest = function()
{
alert("here");
}
}
}
t.nestedOne.nest();
However this is not working (obviously). I would greatly appreciate if someone could point me in the right direction!
That is simply done with:
var t = {
nestedOne: {
nest: function() {
alert('here');
}
}
};
Your code otherwise doesn't make sense. this inside function doesn't refer to the function itself, it refers to the object context that the function is invoked in. And you are not even invoking the functions in your code.
If I say obj.func() then this inside func will be obj for that call. So assigning this.asd = true will assign true to that object's "asd" property.
If you wanted to do a nested class, it looks very different:
ClassA = (function() {
function ClassA() {
}
ClassA.prototype.method1 = function() {
};
function ClassB() {
}
ClassB.prototype.method1 = function() {
};
return ClassA;
}())
only ClassA can now make instances of ClassB. This should achieve same goals as nested classes in java.
See http://jsfiddle.net/CstUH/
function t(){
function f(){
this.nest = function()
{
alert("here");
}
}
this.nestedOne = new f();
}
var myt=new t();
myt.nestedOne.nest()
Edit 1:
You can also use
new t().nestedOne.nest()
instead of
var myt=new t();
myt.nestedOne.nest()
(http://jsfiddle.net/CstUH/1/)
Edit 2:
Or even more condensed:
function t(){
this.nestedOne = new function(){
this.nest = function(){
alert("here");
}
}
}
new t().nestedOne.nest()
http://jsfiddle.net/CstUH/2/
In JS functions are prime class objects, and you can access them directly in the code [i.e. without using reflection or so].
The code you put inside t body would be performed when actually executing t:
t();
You wrote t.nestedOne,nest(), but t has no nestedOne property - you should do like this:
var t = {
nestedOne : {
nest : function()
{
alert("here");
}
}
};
t.nestedOne.nest();
I advice you to have a trip on John Resig's Learning Advanced JavaScript tutorial, it was very enlightening for me.
A simple callback handler I wrote today as an example of how I do deep nesting. I apologize if it's not the bees knees when it comes to code style, it made the concept a little clearer for me.
function test () {
this.that = this;
this.root = this;
this.jCallback = new Array(new Array()); // 2d
this.jCallbackCount = -1;
this.str = "hello";
// Callback handler...
this.command = {
that : this, // let's keep a reference to who's above us on the food chain
root : this.root, // takes us back to the main object
// add : function() { var that = this; console.log(that.that.str); },
add : function(targetFnc, newFunc) {
var that = this;
var home = that.that; // pretty much root but left in as an example of chain traversal.
var root = this.root; // useful for climbing back up the function chain
// console.log(that.that.str);
home.jCallbackCount++;
// target, addon, active
home.jCallback[home.jCallback.length] = { 'targetFunc' : targetFnc, 'newFunc' : newFunc, 'active' : true, 'id': home.jCallbackCount};
console.log('cbacklength: ' + home.jCallback.length);
console.log('added callback targetFunction:[' + targetFnc + ']');
return home.jCallbackCount; // if we want to delete this later...
},
run : function(targetFnc) {
var that = this;
var home = that.that;
console.log('running callback check for: ' + targetFnc + ' There is : ' + (home.jCallbackCount + 1) + 'in queue.');
console.log('length of callbacks is ' + home.jCallback.length);
for(i=0;i < home.jCallback.length - 1;i++)
{
console.log('checking array for a matching callback [' + targetFnc + ']...');
console.log('current item: ' + home.jCallback[i]['targetFunc'] );
if( home.jCallback[i]['targetFunc'] == targetFnc )
{
// matched!
home.jCallback[i]['newFunc']();
}
// console.log(that.that.jCallback[i].targetFunction);
}
}
};
}
test.prototype = {
say : function () {
var that = this;
console.log('inside');
// that.command('doSay');
that.command.run('doSay');
console.log(that.str);
}
} // end proto
// BEGIN TESTING **************************************************************************
// BEGIN TESTING **************************************************************************
// BEGIN TESTING **************************************************************************
var testing = new test();
testing.command.add('doSay', function () { console.log('213123123'); } );
testing.command.add('doSay', function () { console.log('12sad31'); } );
testing.command.add('doSay', function () { console.log('asdascccc'); } );
testing.say();
live:
http://jsfiddle.net/Ps5Uf/
note: to view console output, just open inspector in chrome and click on the "console" tab.
I have a json object retrieved from server in my $(document).ready(...); that has an string that I would like to resolve to a function also defined within $(document).ready(...); so, for example:
$(document).ready(function{
$.getJSON(/*blah*/,function(data){/*more blah*/});
function doAdd(left,right) {
return left+right;
}
function doSub(left,right) {
return left-right;
}
});
with json string:
{"doAdd":{"left":10,"right":20}}
One way I thought about was creating an associative array of the function before loading the json:
var assocArray=...;
assocArray['doAdd'] = doAdd;
assocArray['doSub'] = doSub;
Using eval or window[](); are no good as the function may not be called for some time, basically I want to link/resolve but not execute yet.
Change your JSON to
{method: "doAdd", parameters : {"left":10,"right":20}}
Then do
var method = eval(json.method);
// This doesn't call it. Just gets the pointer
Or (haven't tried this)
var method = this[json.method]
How about something like this?
$(function(){
// Function to be called at later date
var ressolvedFunc = null;
// Ajax call
$.getJSON(/*blah*/,function(data){
// Generate one function from another
ressolvedFunc = (function(data) {
var innerFunc;
var left = data.left;
var right = data.right;
// Detect action
for (action in data) {
if (action == "doAdd")
innerFunc = function() {
return left + right;
};
else
innerFunc = function() {
return left - right;
};
}
return innerFunc;
})(data);
});
});
The anonymous function returns fresh function, with the new values stored within the enclosure. This should allow you to call the function at later date with the data previously retrieved from the GET request.
Rich
try this:
var doX = (function() {
var
data = [],
getDo = function(action) {
for(var d in data) {
if (data[d][action]) {
return data[d];
}
}
return null;
};
return {
set: function(sdata) {
data.push(sdata);
},
doAdd: function() {
var add = getDo("doAdd");
if (!add)
return 0;
return add.doAdd.left + add.doAdd.right;
},
doSub: function() {
var sub = getDo("doSub");
if (!sub)
return 0;
return sub.doAdd.left + sub.doAdd.right;
}
};
})();
$(document).ready(function{
$.getJSON(/*blah*/,function(data){ doX.set(data); });
});