Display inventory counters in multiple locations on the same page

Question

This script works great as a stock countdown, but I can't display it in more than 1 spot on the same page.

For example, there are 4 or 5 products/plans on the same page, each product displays a different inventory quantity, and the time when the quantity changes is also different. Shown on only 1 product.

<span class="qty" id="qty"></span>

<script>
    const setQty = (qty) => {
        qtySpan.innerHTML = qty;

        if (qty == 0) return;

        let parts = Math.floor((Math.random() * 3) + 1);
        if (parts > qty) parts = qty;

        const msec =  Math.floor(((Math.random() * 15) + 15) * 1000);
        qty -= parts;

        // Save the updated quantity in localStorage
        localStorage.setItem('saved_countdown', qty);

        setTimeout(() => setQty(qty), msec);
    }

    // Get the saved countdown value from localStorage, or use default value of 57 if not found
    const defaultQty = localStorage.getItem('saved_countdown') ?? 57;
    
    const qtySpan = document.getElementById('qty');

    // Set the initial value of the quantity
    setQty(defaultQty);
</script>

I copied the script 4x and changed the ID "qty" to qty1, qty2, qty3 and qty4 but it doesn't work, it only shows up in 1 product...:/

Can anyone here help me? Thanks!

Answer 1

I changed the functionality so that you can have multiple countdowns.

const setQty = (qtySpan, qty) => {
qtySpan.innerHTML = qty;

if (qty == 0) return;

let parts = Math.floor((Math.random() * 3) + 1);
if (parts > qty) parts = qty;

const msec = Math.floor(((Math.random() * 15) + 15) * 1000);
qty -= parts;

// Save the updated quantity in localStorage
localStorage.setItem('saved_countdown', qty);

setTimeout(() => setQty(qty), msec);
}

const defaultQty = localStorage.getItem('saved_countdown') ?? 57;

let listOfQty = document.querySelectorAll('.qty');
listOfQty.forEach((qty) =>{
    setQty(qty, defaultQty);

})

You just send the specific number for each countdown as the second parameter.

Answer 2

I've modified your script to a custom element. This means you can now create an element called <stock-counter>.

This element has 2 attributes, quantity and storage-key.

1. quantity is the amount to start counting from.
2. storage-key is the name of the local storage key used to store the last count for this specific counter. If a storage key is set and a storage value is found, that value replaces the quanitity value, unless the storage value is 0.

So the element looks like this:

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You can place any number of these elements on the page and modify the quantity and storage-key of each element.

customElements.define('stock-counter', class extends HTMLElement {
  get quantity() {
    // Check if value has been stored.
    if (this.storageKey !== null) {
      const value = Number(localStorage.getItem(this.storageKey));

      // Use that value if it is a valid number and not 0.
      if (!Number.isNaN(value) && value !== 0) {
        return value;
      }
    }

    // Otherwise get the value from the quantity attribute.
    const value = Number(this.getAttribute('quantity'));

    if (Number.isNaN(value)) {
      return 0;
    }

    return value;
  }

  set quantity(value) {
    if (!isNaN(value)) {
    
      // Store the new value if it's possible.
      if (this.storageKey !== null) {
        localStorage.setItem(this.storageKey, value);
      }

      // Set the new attribute value.
      this.setAttribute('quantity', value);
    }
  }

  get storageKey() {
    return this.getAttribute('storage-key');
  }

  connectedCallback() {
    this.count();
  }

  count = () => {
    const qty = this.quantity;
    this.textContent = qty;

    if (qty === 0) {
      return;
    }

    let parts = Math.floor((Math.random() * 3) + 1);

    if (parts > qty) {
      parts = qty;
    }

    this.quantity -= parts;

    const msec = Math.floor(((Math.random() * 15) + 15) * 1000);
    setTimeout(this.count, msec);
  };
});

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