How do I implement press and hold button javascript?
Solution 1
This code should do everything you're looking for; it's based very loosely on tj111's example. I tried to make it as reusable as possible, and it doesn't need JavaScript mixed in with the HTML.
You do need to add IDs to the buttons (btnUP
and btnDOWN
) and text field (amount
). You can change these IDs in the window.onload
statement.
// This function creates a closure and puts a mousedown handler on the element specified in the "button" parameter.
function makeButtonIncrement(button, action, target, initialDelay, multiplier){
var holdTimer, changeValue, timerIsRunning = false, delay = initialDelay;
changeValue = function(){
if(action == "add" && target.value < 1000)
target.value++;
else if(action == "subtract" && target.value > 0)
target.value--;
holdTimer = setTimeout(changeValue, delay);
if(delay > 20) delay = delay * multiplier;
if(!timerIsRunning){
// When the function is first called, it puts an onmouseup handler on the whole document
// that stops the process when the mouse is released. This is important if the user moves
// the cursor off of the button.
document.onmouseup = function(){
clearTimeout(holdTimer);
document.onmouseup = null;
timerIsRunning = false;
delay = initialDelay;
}
timerIsRunning = true;
}
}
button.onmousedown = changeValue;
}
//should only be called after the window/DOM has been loaded
window.onload = function() {
makeButtonIncrement(document.getElementById('btnUP'), "add", document.getElementById('amount'), 500, 0.7);
makeButtonIncrement(document.getElementById('btnDOWN'), "subtract", document.getElementById('amount'), 500, 0.7);
}
Solution 2
This is kind of quick and dirty, but it should give you a start. Basically you want to set up a few initial "constants" that you can play with to get the desired behavior. The initial time between increments is 1000 ms, and on each iteration if become 90% of that (1000, 990, 891, ... 100) and stops getting smaller at 100 ms. You can tweak this factor to get faster or slower acceleration. The rest I believe is pretty close to what I think you were going for. It seems like you were just missing the event assignments. In the window.onload
you'll see that i assign the onmouseup
, and onmousedown
events to functions that just call the increment()
or decrement()
functions with your initial timeout, or the ClearTimeout()
function to stop the counter.
EDIT: I changed this slightly to fix the bug. Now if you move your mouse pointer off the button and release it will stop the counter.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
<head>
<title><!-- Insert your title here --></title>
<script>
// Fake Constants
var INITIAL_TIME = 1000;
var ACCELERATION = .9;
var MIN_TIME = 100;
// create global variables to hold DOM objects, and timer
var up = null,
down = null,
count = null,
timer = null;
// Increment the counter
function increment (time) {
// decrease timeout by our acceleration factor, unless it's at the minimum
time = (time * ACCELERATION > MIN_TIME) ? (time * ACCELERATION) : MIN_TIME;
count.value ++ ;
// set the timeout for the next round, and pass in the new smaller timeout
timer = setTimeout(
function () {
increment(time);
}, time);
}
// Same as increment only subtracts one instead of adding.
// -- could easily make one function and pass an pos/neg factor instead
function decrement (time) {
time = time * ACCELERATION > MIN_TIME ? (time * ACCELERATION) : MIN_TIME;
count.value --;
timer = setTimeout(
function () {
decrement(time);
}, time);
}
// Initialize the page after all the forms load
window.onload = function () {
// initialization function
// assign DOM objects to our vars for ease of use.
up = document.getElementById('up_btn');
down = document.getElementById('dwn_btn');
count = document.getElementById('count');
// create event handlers for mouse up and down
up.onmousedown = function () {
increment(INITIAL_TIME);
}
down.onmousedown = function () {
decrement(INITIAL_TIME);
}
document.onmouseup = function () {
clearTimeout(timer);
}
}
</script>
</head>
<body>
<!-- Insert your content here -->
<form name="the_form">
<input type="button" value="Up" id="up_btn" /><br />
<input type="button" value="Down" id="dwn_btn" /></br>
<br />
Count:
<input type="text" value="0" id="count" />
</form>
</body>
</html>
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couchua
Updated on April 19, 2022Comments
-
couchua about 2 years
I'm a complete novice, looking for instructions on implementing javascript. I am attempting to replace a YUI slider with buttons and a text field. I am trying to achieve buttons that, when held down, will continue to make the text field increase, preferably at a faster and faster rate. (http://www.blackbird502.com/white.htm)I have this in the java tag in the head:
function holdit(btn, action, start, speedup) { var t; var repeat = function () { action(); t = setTimeout(repeat, start); start = start / speedup; } btn.mousedown = function() { repeat(); } btn.mouseup = function () { clearTimeout(t); } /* to use */ holdit(btn, function () { }, 1000, 2); /* x..1000ms..x..500ms..x..250ms..x */
I have no clue how to implement the press and hold into the following in the body:
<form><input type=button value="UP" class="btn" onClick="javascript:this.form.amount.value++;"><br /><input type=text name=amount value=5 class="text"><br /> <input type=button value="DOWN" class="btn" onClick="javascript:this.form.amount.value--;" ></form>
Is it possible? Thanks.
-
Jesse Brown about 15 yearsOoops, my code sets the onmouseup event to the button so has the bug that SydneySM refers to in his solution.
-
couchua about 15 yearsI just worked this into the page, and it works perfectly: blackbird502.com/white1.htm I will try out SidneySM's below to try and avoid the 'bug,' though there is no evidence of a 'bug' from a novice's stand point. THANKS!
-
Jesse Brown about 15 yearsI changed the code to fix the bug. I just attached the onmouseup event to the document. Credit goes to SidneySM for catching that.