This question already has answers here:
setTimeout in for-loop does not print consecutive values [duplicate]
(10 answers)
Closed 7 years ago.
I want a string to appear character-for-character with the following code:
function initText()
{
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
for(c = 0; c < text.length; c++)
{
setTimeout('textScroller.innerHTML += text[c]', 1000);
}
}
window.onload = initText;
It's not working.. what am I doing wrong?
Try something like this:
function initText()
{
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
var c = 0;
var interval = setInterval(function() {
textScroller.innerHTML += text[c];
c++;
if(c >= text.length) clearInterval(interval);
}, 1000);
}
Note I added clearInterval to stop it when it's needed.
Currently, you are defining 18 timeouts and all will be executed ~ at once.
Second problem is, you pass instructions to execute as a String. In that case, the code won't have access to all variables defined in initText, because evaluated code will be executed in global scope.
IMO, this should do the job
function initText(){
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
var c = 0;
(function(){
textScroller.innerHTML += text.charAt(c++);
if(text.length > c){
setTimeout(arguments.callee, 1000);
}
})();
}
Even more generic than answer by #yauhen-yakimovich:
Using Timeout:
var repeat = (function () {
return function repeat(cbWhileNotTrue, period) {
/// <summary>Continuously repeats callback after a period has passed, until the callback triggers a stop by returning true. Note each repetition only fires after the callback has completed. Identifier returned is an object, prematurely stop like `timer = repeat(...); clearTimeout(timer.t);`</summary>
var timer = {}, fn = function () {
if (true === cbWhileNotTrue()) {
return clearTimeout(timer.t); // no more repeat
}
timer.t = setTimeout(fn, period || 1000);
};
fn(); // engage
return timer; // and expose stopper object
};
})();
Using Interval:
var loop = (function () {
return function loop(cbWhileNotTrue, period) {
/// <summary>Continuously performs a callback once every period, until the callback triggers a stop by returning true. Note that regardless of how long the callback takes, it will be triggered once per period.</summary>
var timer = setInterval(function () {
if (true === cbWhileNotTrue()) clearInterval(timer);
}, period || 1000);
return timer; // expose stopper
};
})();
Slight difference between the two indicated in comments -- the repeat method only repeats after the callback performs, so if you have a "slow" callback it won't run every delay ms, but repeats after every delay between executions, whereas the loop method will fire the callback every delay ms. To prematurely stop, repeat uses an object as the returned identifier, so use clearTimeout(timer.t) instead.
Usage:
Just like answer by #soufiane-hassou:
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
var c = 0;
var interval = repeat/* or loop */(function() {
textScroller.innerHTML += text[c];
c++;
return (c >= text.length);
}, 1000);
As mentioned, premature stopping would be:
/* if repeat */ clearTimeout(interval.t);
/* if loop */ clearInterval(interval);
Try this:
function initText()
{
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
for(c = 0; c < text.length; c++)
{
setTimeout("textScroller.innerHTML += '" + text[c] + "'", 1000 + c*200);
}
}
window.onload = initText;
Try using a closure:
function init() {
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
var c = 0;
function run() {
textScroller.innerHTML += text[c++];
if (c<text.length)
setTimeout(run, 1000);
}
setTimeout(run, 1000);
}
init()
The problem in your code is that the code you put in the string will run in the global context, where textScroller is not defined (it is defined inside your function).
I want to share a snippet (based on answer by Soufiane Hassou). It extends to the case when you literally replace a for-loop body to be iterated over some array in a fixed interval of time. Basically same synchronous loop but with "sleep" pausing (because javascript is not a synchronous programming language).
function loop(arr, take, period) {
period = period || 1000;
var i = 0;
var interval = setInterval(function() {
take(i, arr[i]);
if (++i >= arr.length) { clearInterval(interval);}
}, period);
}
Usage example:
loop([1, 2, 3, 4], function(index, elem){
console.log('arr[' + index + ']: ' + elem);
});
Tested in Node JS. Hope that helps someone.
edit>
the following update makes code usable together with libs doing heavy "prototyping" (like jQuery or prototype):
function loop(arr, take, period) {
period = period || 1000;
var scope = {
i: 0,
arr: arr,
take: take,
};
var iterate = (function iterate() {
if (this.i >= this.arr.length) { clearInterval(this.interval); return}
take(this.i, this.arr[this.i++]);
}).bind(scope);
scope.interval = setInterval(iterate, period);
}
Your for loop is setting a timeout for every character at once, so they will not appear in sequence, but all at once. Your setTimeout should include code to another setTimeout that will include the next character to display.
So something like this (didn't test this)
function initText()
{
var textScroller = document.getElementById('textScroller');
var text = 'Hello how are you?';
setTimeout('nextChar(text)', 1000);
}
function nextChar(text){
if(text.length > 0){
textScroller.innerHTML += text[0];
setTimeout('nextChar(text.substring(1))', 1000);
}
}
If you want to preserve setTimeOut (instead of setInterval) and use named function (instead of evaluating code block in setTimeOut call), then this could be helpful:
var b = {
textScroller: document.getElementById('textScroller'),
text: "Hello how are you?"
};
function initText() {
for(c = 0; c < b.text.length; c++) {
setTimeout("append("+c+")", 1000 + c*200);
}
}
function append(c) {
b.textScroller.innerHTML += b.text[c];
}
window.onload = initText;
With the above you can pass a parameter to append function.
To pass several parameters the next code does the trick:
var glo = [];
function initText()
{
var textScroller = document.getElementById('textScroller');
var text = "Hello how are you?";
var timeout_time;
for(c = 0; c < text.length; c++) {
glo[glo.length] = {text:text, c:c, textScroller:textScroller};
timeout_time = 1000 + c * 200;
setTimeout("append(" + (glo.length - 1) + ")", timeout_time);
}
}
function append(i)
{
var obj = glo[i];
obj.textScroller.innerHTML += obj.text[obj.c];
obj = null;
glo[i] = null;
}
window.onload = initText;
With the above you have only one global array glo. In loop you create new array members to glo and in append() function refer to these members using index which is passed as parameter.
CAUTION: the second code sample is not meant as best or most suitable solution to OP:s problem, but may benefit in other setTimeOut relative problems, eg. when someone wants to make a presentation or performance test where some functionalities are needed to call after some delay. The advantage of this code is to make use of for loops (many coders want to use for loops) and the possibility to use also inner loops and the ability to "send" local variables in their loop time state to timeOut functions.
May be better to loop in cascade. For exemple to fade a div :
div=document.createElement('div');
div.style.opacity=1;
setTimeout(function(){fade(1);},3000);
function fade(op){
op-=.05;
if(op>0) setTimeout(function(){div.style.opacity=op;fade(op);},30);
else document.body.removeChild(div);
}
Related
I have memoized lodash function that takes an object as its argument. When this function gets called, how can I tell how often its hitting the cache vs evaluating the function with new arguments?
If you're just doing it in development, you can do something like count the number of times cache.get is called vs how many times the function is called. Something like
var calls = 0;
var hits = 0;
function test(b) {
calls += 1;
return b + 1;
}
var mem_test = _.memoize(test);
mem_test.cache.get = function(n) {
var cached = mem_test.cache.get;
calls += 1;
hits += 1;
return function() {
var result = cached.call(this, n);
return result;
}
}
mem_test(1);
mem_test(2);
mem_test(2);
console.log(calls);
console.log(hits);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>
That simple example should output 3 and 1.
I need to randomly change characters of a text and after some delay fix them.
There is my code:
<h1 id="text" style="margin-top:100px;">SOME TEXT</h1>
<script>
var text = document.getElementById("text").innerHTML.split("");
var myArr = text;
for (i = 0; i < myArr.length; ++i) {
var handle = setInterval(function () { xyz(i) }, 100);
setTimeout(function (handle) {
myArr[i] = text[i];
clearInterval(handle);
}, (i) * 1000);
}
function xyz(index) {
myArr[index] = String.fromCharCode(Math.random() * 26 + 65);
document.getElementById("text").innerHTML = myArr;
}
</script>
It seems i have no a good understanding of how setInterval work! :(
EDIT:
With my code only text[text.length+1] character has change that mean passed parameter to xyx() function is last value of loop counter variable (after loop over). Now my question is how trigger setInterval() function with i = 0 ,1 ... , text.length.
Can someone guide me?
basicly setInterval execute a function with a iteration in time. and setInterval gives you a promise to cancel it any time you want.
var myPromise = setInterval(function(){
//some code here
},delayMiliseconds);
to cancel this code
clearInterval(myPromise);
Related to this question problem was wrong way to passing arguments to setInterval().the callback function i passed to setInterval() maintains a reference to "i" rather than the snapshot value of "i" as it existed during each particular iteration...
<h1 id="text" style="margin-top:100px;">SOME TEXT</h1>
<script>
var text = document.getElementById("text").innerHTML.split("");
var myArr = document.getElementById("text").innerHTML.split("");
for (i = 0; i < text.length; i++) {
var handle = setInterval(function (k) { xyz(k) }, 100,i);
setTimeout(function (handle, i) {
console.log(i);
console.log(text[i]);
myArr[i] = text[i];
clearInterval(handle);
}, (i) * 1000,handle,i);
}
function xyz(index) {
myArr[index] = String.fromCharCode(Math.random() * 26 + 65);
document.getElementById("text").innerHTML = myArr.toString();
}
</script>
Please find my code below.
for (i= 0; i < region.length; i++) {
point = region[i];
animation = setInterval(function () {
..........
}, 12);
}
I want to execute the codes in setInterval before i value changes from 0 to 1. But currently after all the execution of for loop only, codes in the setInterval method is getting executed. is there any way to achieve my requirement.
Use closure inside for loop:
(function(i) {
setInterval(function() {
console.log("inside setinterval" + i)
}, 10);
})(i)
hope this solves your problem
Async loop you need:
var len = region.length;
var i = 0;
var animate = function(){
setTimeout(function () {
point = region[i];
//do something..........
if (i++ < len) animate();
}, 12);
};
You should use recursion for such requirements. Also, you should use setTimeout as setInterval will run for eternity(till page exists) until you clear it.
var i = 0;
var MAX_COUNT = 10;
function doSomething(str){
console.log(str);
processData();
}
function initSetTimeout(callback){
setTimeout(callback, 1000)
}
function processData(){
if(++i<MAX_COUNT)
initSetTimeout(doSomething.bind(null, i))
}
processData()
I have some words like "beautiful","awesome","nice" and "wonderful".
i want to show the each word as typing text effect one after one for infinite time.
see i want like this :google forms
I have made the running text effect.
see the code below:
var myText= "beautiful";
var text = myText.split("");
var counter = 0;
function typeIt(text){
var SI=setInterval(function(){
var h1 = $("#myTypingText");
h1.append(text[counter]);
counter++;
if(counter==text.length){
clearInterval(SI);
}
},70);
}
i am not able to run this function for each word one after one for infinite time.
please help me to resolve this.
thanks in advance.
You can modify your existing function to accept an array of words, and process the words one by one.
EDIT: Expand this first snippet to see my original answer that has no delay in between words:
function typeIt(words) {
var letterIndex = 0;
var wordIndex= 0;
var h1 = $("#myTypingText");
var SI = setInterval(function() {
if (letterIndex === words[wordIndex].length) { // if at end of current word
wordIndex = (wordIndex + 1) % words.length; // go to next word
letterIndex = 0;
h1.empty(); // clear output div
}
h1.append(words[wordIndex][letterIndex]);
letterIndex++;
}, 70);
}
typeIt(["beautiful", "awesome", "nice", "wonderful"]);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="myTypingText"></div>
Note that you don't need to .split("") the word, because you can directly reference the individual characters in a string with the same square-bracket syntax as referencing array elements, e.g., "text"[2] is "x".
You can use setTimeout() to control the delay in between words:
function typeIt(words) {
var letterIndex = 0;
var wordIndex = 0;
var h1 = $("#myTypingText");
(function nextWord() {
var SI = setInterval(function() {
h1.append(words[wordIndex][letterIndex]);
letterIndex++;
if (letterIndex === words[wordIndex].length) {
wordIndex = (wordIndex + 1) % words.length;
letterIndex = 0;
clearInterval(SI);
setTimeout(function() {
h1.empty();
nextWord();
}, 1000); // delay between words
}
}, 70); // delay between letters
})();
}
typeIt(["beautiful", "awesome", "nice", "wonderful"]);
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<div id="myTypingText"></div>
Note that this isn't necessarily the cleanest way to structure the code, but it seemed the quickest way to modify what you already had to achieve the desired output.
Further reading: Immediately Invoked Function Expressions (IIFEs).
I have this function which loops through a list of strings every 5 seconds. I would like it to stay on the last string after finishing the loop.
What do I need to change here?
window.specialWorkBoxStyleOverride = function(workBox) {
var statusTextBox = $("<div class = 'status-description-box'></div>");
$(workBox).append(statusTextBox);
var statusTexts = ["Checking", "Updating", "Processing", "Saving"];
var idx = 0;
var updateStatus = function() {
statusTextBox.text(statusTexts[idx]);
idx = (idx + 1) % statusTexts.length;
setTimeout(updateStatus, 5000);
};
updateStatus();
};
Thanks a lot.
Right now your code always calls setTimeout, so it will loop forever. Checking whether you've reached the end of your list should be sufficient to stop this (and means you don't need the modular arithmetic any more):
var updateStatus = function() {
statusTextBox.text(statusTexts[idx]);
idx++;
if (idx < statusTexts.length) {
setTimeout(updateStatus, 5000);
}
};