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Javascript - get button data attribute value, push into array and calculate

Lurker and new to posting here.

I'm looking for a solution to this:

<a points="0" href="#" class="btn">Button Text</a>
<a points="1" href="#" class="btn">Button Text</a>
<a points="2" href="#" class="btn">Button Text</a>

<div class="success"></div>
<div class="failure"></div>

I need to find a way for a function/loop, to add the data attribute value (points) into an array, and calculate that if the result is >3 to show the "success" div, else to hide it and show the "failure" div.

I've no idea where to start honestly here and would appreciate help. I searched online for some results to put some code together but there wasn't too much on grabbing data attribute value on click and pushing it into an array.

Thanks in advance!

about 4 years ago · Juan Pablo Isaza

2 answers

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points is not any attribute. For custom attributes use data-*, hence data-points.

Here is a basic example (based on assumptions) as to how you should go about it.

let newArr = [...document.querySelectorAll('a')];

let sum = newArr.reduce((cum,x) => {
        return cum + Number(x.getAttribute('data-points'));
},0);

console.log(sum);

if(sum > 3){
 document.querySelector('.success').style.display = 'block';
 document.querySelector('.failure').style.display = 'none';
}
else{
document.querySelector('.success').style.display = 'none';
document.querySelector('.failure').style.display = 'block';
}

<a data-points="0" href="#" class="btn">Button Text</a>
<a data-points="1" href="#" class="btn">Button Text</a>
<a data-points="2" href="#" class="btn">Button Text</a>
<a data-points="3" href="#" class="btn">Button Text</a>
<div class="success">Success</div>
<div class="failure">Failure</div>

Get all relevant a elements using querySelectorAll.
Compute the sum using reduce and getAttribute
Use style.display to modify the styles.

about 4 years ago · Juan Pablo Isaza Report

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Accepted Answer · 2022-07-13T06:22:25.843Z

From my comments:

use data-points to adhere to standard. points is not a standard attribute
Also on what event do you add? Why do you need to add if you already know the number on the server? –
Lastly look at classList.toggle:

let result = [];
document.addEventListener("click", function(e) {
  const tgt = e.target;
  if (tgt.classList.contains("btn")) {
    result.push(+tgt.dataset.points)
  }
  if (tgt.id === "last") {
    const sum = result.reduce((a, b) => a + b)
    document.querySelector('.success').classList.toggle('hide', sum < 3)
    document.querySelector('.failure').classList.toggle('hide', sum >= 3)
  }
})

.hide {
  display: none;
}

<a data-points="0" href="#" class="btn">Button Text</a>
<a data-points="1" href="#" class="btn">Button Text</a>
<a data-points="2" href="#" class="btn">Button Text</a>
<a data-points="3" href="#" id="last" class="btn">Button Text</a>
<div class="success hide">Success</div>
<div class="failure hide">Failure</div>

Old answer:

let sum = [...document.querySelectorAll('a[data-points]')]
  .map(anchor => +anchor.dataset.points)
  .reduce((a, b) => a + b)

document.querySelector('.success').classList.toggle('hide', sum < 3)
document.querySelector('.failure').classList.toggle('hide', sum >= 3)

.hide {
  display: none;
}

<a data-points="0" href="#" class="btn">Button Text</a>
<a data-points="1" href="#" class="btn">Button Text</a>
<a data-points="2" href="#" class="btn">Button Text</a>
<a data-points="3" href="#" class="btn">Button Text</a>
<div class="success">Success</div>
<div class="failure">Failure</div>

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Javascript - get button data attribute value, push into array and calculate

2 answers

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Andres GPT