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snippets/js/s/counter.md

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+---
+title: Counter
+type: snippet
+language: javascript
+tags: [browser]
+cover: touch-flower
+dateModified: 2020-11-01T20:50:57+02:00
+---
+
+Creates a counter with the specified range, step and duration for the specified selector.
+
+- Check if `step` has the proper sign and change it accordingly.
+- Use `setInterval()` in combination with `Math.abs()` and `Math.floor()` to calculate the time between each new text draw.
+- Use `Document.querySelector()`, `Element.innerHTML` to update the value of the selected element.
+- Omit the fourth argument, `step`, to use a default step of `1`.
+- Omit the fifth argument, `duration`, to use a default duration of `2000`ms.
+
+```js
+const counter = (selector, start, end, step = 1, duration = 2000) => {
+  let current = start,
+    _step = (end - start) * step < 0 ? -step : step,
+    timer = setInterval(() => {
+      current += _step;
+      document.querySelector(selector).innerHTML = current;
+      if (current >= end) document.querySelector(selector).innerHTML = end;
+      if (current >= end) clearInterval(timer);
+    }, Math.abs(Math.floor(duration / (end - start))));
+  return timer;
+};
+```
+
+```js
+counter('#my-id', 1, 1000, 5, 2000);
+// Creates a 2-second timer for the element with id="my-id"
+```