I'm using code from a JSFiddle to implement a count up feature on my site. I like it because it allows me to target a number displayed in a specific div, and I don't need to specify that number in the javascript, which means I can use it on any page for any number I choose.
See the code here:
// basic class implementation
function myCounter() {
// privileged property for iteration
this.i = 0;
// privileged init method
this.init();
}
// defining init method
myCounter.prototype.init = function () {
// reassign this
var _this = this;
setInterval(function () {
// call this.countUp() using our new created variable.
// this has to be done as this would normally call something
// inside this function, so we have to pass it as own
// variable over
_this.countUp();
}, 500);
clearInterval(function () {
this.i ==
};
};
// defining the counter method
myCounter.prototype.countUp = function () {
this.i++;
document.getElementById('counter').innerHTML = this.i;
};
// create a new instance of our counter class
var counter = new myCounter();
The only problem is that it doesn't stop counting. I'd love to add some code for that myself, except I'm not familiar enough with javascript and have no idea where to start.
Is there a way to tell javascript to stop counting at the number specified in the targeted div?
Thanks so much!
// basic class implementation
function myCounter() {
// privileged property for iteration
this.i = 0;
// privileged init method
this.init();
}
// defining init method
myCounter.prototype.init = function () {
// reassign this
var _this = this;
this.timer = setInterval(function () {
// call this.countUp() using our new created variable.
// this has to be done as this would normally call something
// inside this function, so we have to pass it as own
// variable over
_this.countUp();
}, 500);
};
// defining the counter method
myCounter.prototype.countUp = function () {
this.i++;
document.getElementById('counter').innerHTML = this.i;
// stop the timer
if(this.i == 8){
clearInterval(this.timer)
}
};
// create a new instance of our counter class
var counter = new myCounter();
Related
I have tried different things but I do seem to be looking something over that is too obvious. Trying to use the value a function(method) returns inside an object and use it in another method with setTimeout within that same object.
This is the html:
<h1>3000</h1>
The javascript (jQuery in this case):
var foo = {
getValue: function() {
var h1Text = $('h1').text();
h1Text = parseInt(h1Text);
return h1Text;
},
useValue: function() {
var time = this.getValue();
var alertIt = alert('Hello');
setTimeout(alertIt,time);
}
};
foo.useValue();
// log shows correct value
console.log(foo.getValue());
// returns a number
console.log(typeof(foo.getValue()));
The alert does show up, but on load rather than using those 3 seconds.
It does log the correct value and also says it's a number so I'm really not sure what I am doing wrong. Any help is appreciated. Thanks
In useValue() you call alert('Hello'), so it's executed immediately and the result is stored in alertIt variable. You should put it inside the function like this, as setTimeout expects a function as a first parameter:
var alertIt = function() {
alert('Hello');
}
setTimeout(alertIt,time);
setTiimeout expects function and not variable.
Also var alertIt = alert('Hello'); this will return undefined.
Note: var a = function() will call it and assign return value. To assign a function to a variable with parameter, use .bind
Try alert.bind(null, "hello");
For demo purpose, I have hardcoded value of delay and commented getValue code.
var foo = {
getValue: function() {
//var h1Text = $('h1').text();
//h1Text = parseInt(h1Text);
return true// h1Text;
},
useValue: function() {
var time = 3000//this.getValue();
var alertIt = alert.bind(null,'Hello');
setTimeout(alertIt, time);
}
};
foo.useValue();
// log shows correct value
console.log(foo.getValue());
// returns a number
console.log(typeof(foo.getValue()));
I'm trying to create a simple game loop and trying to use OOP paradigm in JS. Here is my code:
HTML
<body onload="Game.OnLoad('gameField')" onkeydown="Game.KeyDown(event)">
<p id="info">1</p>
<p id="info2">2</p>
<canvas id="gameField"
width="896px"
height="717px"
class="game-field"
style="border: 4px solid aqua"
onclick="Game.MouseClick(event)"></canvas>
</body>
JavaScript
// class Timer
// version: 1
// only tick() functionality available
// right now
function Timer() {
var date = new Date();
var prevTick = 0;
var currTick = 0;
// update timer with tick
this.tick = function() {
prevTick = currTick;
currTick = date.getTime();
}
// get time between two ticks
this.getLastTickInterval = function() {
return currTick - prevTick;
}
}
// global object Game
// which handles game loop
// and provide interfaces for
var Game = new function() {
// variables:
this.canvas = 0;
var gameLoopId = 0;
this.timer = new Timer();
// events:
this.KeyDown = function(e) {}
// game loop:
this.Run = function() {
this.timer.tick();
this.Update(this.timer.getLastTickInterval());
this.Draw();
}
this.Update = function(dt) {
document.getElementById("info").innerHTML = dt;
}
this.Draw = function() {}
this.StopGameLoop = function() {
clearInterval(gameLoopId);
}
this.OnLoad = function(canvasName) {
this.canvas = document.getElementById(canvasName);
this.timer.tick();
// start game loop
setInterval(this.Run, 1000);
}
}
(Fiddle)
I'm trying to make Game class global. Other classes must be instantinated using new.
Classes Game and Timer are placed in different files called Game.js and Timer.js. When I run this code in Chrome I got an error in DevTools: "Uncaught TypeError: Cannot call method 'tick' of undefined" in Game.Run function at the line this.timer.tick();
So I wonder, what is the problem with my code? Thanks for reply.
Your problem is with the context. When you're calling tick this is window, not Game.
You can handle this, for example, by setting:
var self = this;
this.Run = function() {
self.timer.tick();
self.Update(self.timer.getLastTickInterval());
self.Draw();
}
Few things to consider in your code :
Concerning your issue, methode like setInterval or setTimeout loose the context. Easiest solution is to bind a context to the callback :
setInterval(this.Run.bind(this), 1000);
Secondly, avoid adding private methode inside an object function. In that case, every instance of Game will have its own set of functions (memory leak).
Prefer using prototypes :
function Game () {
this.canvas = null;
}
Game.prototype = {
init: function() {}
render: function () {}
};
Lastly, I see you redraw every seconds, which is ok. But if you want 60fps, you can use requestAnimationFrame for drawing oriented loops.
ps: just to be very nitpicking, functions' name should be camelCase so starting with lower case.
I have always had trouble working with time events. Could someone please explain why A doesn't work and B does? The only difference is in A I put the event binding in a function. Don't worry about the function close, it has nothing to do with the question. When I test A, there is no js errors but timer is not cleared.
A ->
Test.Navigation = (function() {
var openTimer = null;
var closeTimer = null;
var addListeners = function() {
$('.hover_container').on('mousemove', function(e) {
clearTimeout(closeTimer);
});
$('.hover_container').on('mouseleave', function(e) {
// set the close timer
var container = this;
closeTimer = setTimeout(function() {
//has the mouse paused
close(container);
}, 750);
});
};
return {
init : function() {
addListeners();
}
};
})();
B ->
Test.Navigation = (function() {
var openTimer = null;
var closeTimer = null;
$('.hover_container').on('mousemove', function(e) {
clearTimeout(closeTimer);
});
$('.hover_container').on('mouseleave', function(e) {
// set the close timer
var container = this;
closeTimer = setTimeout(function() {
//has the mouse paused
close(container);
}, 750);
});
var addListeners = function() {
// nothing here
};
return {
init : function() {
addListeners();
}
};
})();
Edit: Please ignore the container part, it has nothing to dow ith the question it is simply part of the full code that I did not take out
A is binded before the object exists where the init is called. Because your return a new object. If you are using, 2 objects are created. 1 with the vars en binds. and 1 with the returns.
B is working because you create a function where the elements are initialized and use the right scope. A is not working because the bindings are on the wrong scope because your create 2 objects:
new Test.Navigation(); // Create 1 object
// Create second object.
return {
init : function() {
addListeners();
}
};
Youd better get a structure like this, then it should work aswell:
Test.Navigation = (function() {
// Private vars. Use underscore to make it easy for yourself so they are private.
var _openTimer = null,
_closeTimer = null;
$('.hover_container').on('mousemove', function(e) {
clearTimeout(_closeTimer );
});
$('.hover_container').on('mouseleave', function(e) {
// set the close timer,
// use $.proxy so you don't need to create a exta var for the container.
_closeTimer = setTimeout(
$.proxy(function() {
//has the mouse paused
close(this);
}, this)
, 750);
});
this.addListeners = function() {
// nothing here
};
this.init = function() {
this.addListeners();
}
// Always call the init?
this.init();
return this; // Return the new object Test.Navigation
})();
And use it like
var nav = new Test.Navigation();
nav.init();
Also as you can see I upgraded your code a bit. Using $.proxy, _ for private vars.
Your use of this is in the wrong scope for the first approach.
Try
var openTimer = null;
var closeTimer = null;
var self = this;
and then later
var container = self;
In your code for example A,
$('.hover_container').on('mouseleave', function(e) {
// set the close timer
var container = this;
this is actually referring to the current $('.hover_container') element.
Also, since setTimeout will wait before the previous setTimeout finishes to start again, you can get discrepancies. You may want to switch to setInterval because it will issue its callback at every interval set regardless of if the previous callback has completed.
My guess is that in the calling code, you have a statement new Test.Navigation() which, for B, addListeners is called at the time of new Test.Navigation(). In A, you return an object ref that calls an init function. Can you verify that init() is called?
I.e. in A, init() has to be called before the handlers are added. In B, the handlers are added everytime you instantiate Test.Navigation --- which, depending on the calling code, could be bad if you intend to instantiate more than one Test.Navigation() at a time.
I need to know what I am doing wrong because I cannot call the internal functions show or hide?
(function()
{
var Fresh = {
notify:function()
{
var timeout = 20000;
$("#notify-container div").get(0).id.substr(7,1) == "1" && (show(),setTimeout(hide(),timeout));
var show = function ()
{
$("body").animate({marginTop: "2.5em"}, "fast", "linear");
$("#notify-container div:eq(0)").fadeIn("slow");
},
hide = function()
{
$("#notify-container div").hide();
}
}//END notify
}
window.Fresh = Fresh;
})();
Fresh.notify();
thanks, Richard
UPDATE
If you wanted to be able to do something like: Fresh.notify.showMessage(), all you need to do is assign a property to the function notify:
var Fresh = {notify:function(){return 'notify called';}};
Fresh.notify.showMessage = function () { return this() + ' and showMessage, too!';};
Fresh.notify();//notify called
Fresh.notify.showMessage();//notify called and showMessage, too!
This will point to the function object here, and can be called as such (this() === Fresh.notify();). That's all there is too it.
There's a number of issues with this code. First of all: it's great that you're trying to use closures. But you're not using them to the fullest, if you don't mind my saying. For example: the notify method is packed with function declarations and jQuery selectors. This means that each time the method is invoked, new function objects will be created and the selectors will cause the dom to be searched time and time again. It's better to just keep the functions and the dom elements referenced in the closure scope:
(function()
{
var body = $("body");
var notifyDiv = $("#notify-container div")[0];
var notifyDivEq0 = $("#notify-container div:eq(0)");
var show = function ()
{
body.animate({marginTop: "2.5em"}, "fast", "linear");
notifyDivEq0.fadeIn("slow");
};
var hide = function()
{//notifyDiv is not a jQ object, just pass it to jQ again:
$(notifyDiv).hide();
};
var timeout = 20000;
var Fresh = {
notify:function()
{
//this doesn't really make sense to me...
//notifyDiv.id.substr(7,1) == "1" && (show(),setTimeout(hide,timeout));
//I think this is what you want:
if (notifyDiv.id.charAt(6) === '1')
{
show();
setTimeout(hide,timeout);//pass function reference
//setTimeout(hide(),timeout); calls return value of hide, which is undefined here
}
}//END notify
}
window.Fresh = Fresh;
})();
Fresh.notify();
It's hard to make suggestions in this case, though because, on its own, this code doesn't really make much sense. I'd suggest you set up a fiddle so we can see the code at work (or see the code fail :P)
First, you're trying to use show value when it's not defined yet (though show variable does exist in that scope):
function test() {
show(); // TypeError: show is not a function
var show = function() { console.log(42); };
}
It's easily fixable with moving var show line above the point where it'll be called:
function test() {
var show = function() { console.log(42); };
show();
}
test(); // 42
... or if you define functions in more 'traditional' way (with function show() { ... } notation).
function test() {
show();
function show() { console.log(42); };
}
test(); // 42
Second, you should use this instead:
... && (show(), setTimeout(hide, timeout) );
... as it's the function name, and not the function result, that should be passed to setTimeout as the first argument.
You have to define show and hide before, also change the hide() as they said.
The result will be something like this:
(function()
{
var Fresh = {
notify:function()
{
var show = function()
{
$("body").animate({marginTop: "2.5em"}, "fast", "linear");
$("#notify-container div:eq(0)").fadeIn("slow");
},
hide = function()
{
$("#notify-container div").hide();
},
timeout = 20000;
$("#notify-container div").get(0).id.substr(7,1) == "1" && ( show(), setTimeout(hide,timeout) );
}//END notify
}
window.Fresh = Fresh;
})();
Fresh.notify();
I think order of calling show , hide is the matter . I have modified your code . It works fine . Please visit the link
http://jsfiddle.net/dzZe3/1/
the
(show(),setTimeout(hide(),timeout));
needs to at least be
(show(),setTimeout(function() {hide()},timeout));
or
(show(),setTimeout(hide,timeout));
function Something() {
this.var1 = 0;
this.var2 = 2;
this.mytimer;
this.getCars=function() {
//some code
};
this.start = function(l) {
this.updateTimer=setInterval("this.getCars();" , 5000);
};
}
var smth = new Something();
smth.start();
When I type in this.getCars() it does not work. if the function is global declared and i put in for example just getCars it works.
I don't know how to work out this problem because setInterval becomes as parameter a String.
Can somebody help me put with this?
var me = this
setInterval(function() {me.getCars()}, 5000)
if you happen to be using prototype, you could also use the handy bind method:
setInterval(this.getCars.bind(this), 5000)
Try this:
function Something() {
this.var1 = 0;
this.var2 = 2;
this.mytimer;
var me = this;
this.getCars = function() {
console.log(me.var2);
};
this.start = function(l) {
me.updateTimer = setInterval(me.getCars, 1000);
}
}
var smth = new Something();
smth.start();
The console.log() bit is Firefox/Firebug. Replace it with something else if you're not using that (although I would highly recommend developing with it).
Basically the problem is that when you call a function, even a method of an object, the way you call it determines the value of this. See Method binding for more details. So what you do is fix the value of this as I've done in the above example (for methods).