How do I correctly use setInterval and clearInterval to switch between two different functions?

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For practice I am trying to display a number that increments from 0 - 9, then decrements from 9 - 0, and infinitely repeats.

The code that I have so far seems to

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6条回答

借酒劲吻你

2020-12-01 13:14

@Claude, you are right, the other solution I proposed was too different from original code. This is another possible solution, using setInterval and switching functions:

function onloadFunctions() {
    var count = 0;
    var refId = null;
    var target = document.getElementById("aux");

    var countUp = function() {
        target.innerHTML = count;
        count ++;
        if(count >= 9) {
            window.clearInterval(refId);
            refId = window.setInterval(countDown, 500);
        }
    }

    var countDown = function() {
        target.innerHTML = count;
        count --;
        if(count <= 0) {
            window.clearInterval(refId);
            refId = window.setInterval(countUp, 500);
        }
    }
    refId = window.setInterval(countUp, 500);
}

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借酒劲吻你

2020-12-01 13:17

try this:

...
<body onload = "onloadFunctions();">

    <script>
        var cup, cdown; // intervals
        var count = 0,
            here  = document.getElementById("here");

        function onloadFunctions() {
            cup = setInterval(countUp, 200);
        }

        function countUp() {
            here.innerHTML = count;
            count++;

            if(count === 10) {
                clearInterval(cup);
                cdown = setInterval(countDown, 200);
            }
        }
        function countDown() {   
            here.innerHTML = count;
            count--;

            if(count === 0) {
                clearInterval(cdown);
                cup = setInterval(countUp, 200);
            }       
        }
    </script>

    From 0 - 9, up and down:&nbsp;&nbsp;<div id = "here"></div>
</body>

you could also create a single reference to #here element. Use always === instead of ==

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心在旅途

2020-12-01 13:23

clearInterval(this);. You can't do that. You need to save the return value from setInterval.

var interval;
function onloadFunctions()
{
    countUp();
    interval = setInterval(countUp, 200);
}

var count = 0;
function countUp()
{
    document.getElementById("here").innerHTML = count;
    count++;

    if(count == 10)
    {
        clearInterval(interval);
        countDown();
        interval = setInterval(countDown, 200);
    }
}
function countDown()
{
    document.getElementById("here").innerHTML = count;
    count--;

    if(count == 0)
    {
        clearInterval(interval);
        countUp();
        interval = setInterval(countUp, 200);
    }       
}

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春和景丽

2020-12-01 13:24

    /** Tools */
const log = require('ololog').configure({
  locate: false
})

let count = 0
let interval__UP
let interval__DOWN

function countUp () {
  count++
  log.green('countUp(): ', count)

  if (count == 5) {
    clearInterval(interval__UP)
    interval__DOWN = setInterval(function () {
      countDown()
    }, 1000)
  }

}

function countDown () {

  count--
  log.red('countDown(): ', count)

  if (count == 0) {
    clearInterval(interval__DOWN)
    interval__UP = setInterval(function () {
      countUp()
    }, 3000)
  }
}

function start () {
  countUp()
  log.cyan('start()')
  interval__UP = setInterval(function () {
    countUp()
  }, 2000)
}

start()

Console Log shows it's working

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暗喜

2020-12-01 13:30

You need to capture the return value from setInterval( ... ) into a variable as that is the reference to the timer:

var interval;
var count = 0;

function onloadFunctions()
{
    countUp();
    interval = setInterval(countUp, 200);
}

/* ... code ... */

function countUp()
{
    document.getElementById("here").innerHTML = count;
    count++;

    if(count === 10)
    {
        clearInterval(interval);
        countUp();
        interval = setInterval(countUp, 200);
    }
}

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温柔的废话

2020-12-01 13:31

There are many ways to solve this problem, the following is my suggestion:

function onloadFunctions() {
    var count = 0;
    var delta = 1;
    var target = document.getElementById("here");
    var step = function() {
        if(count <= 0) delta =  1;
        if(count >= 9) delta = -1;
        count += delta;
        target.innerHTML = count;
        window.setTimeout(step, 500);
    }
    step ();
}

PS: it's safer to use setTimeout than setInteval.

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