Transition on height using javascript style.height

Question

In order to manipulate height property, so I use javascript not jquery then I got a problem.
The problem is that I cannot override the height back to zero once I have set to the scrollHeight of the element.

Here is my js code:

let isClosed = true;
var cals = document.getElementsByClassName('h-strench-box');

for (var i = 0; i < cals.length; i ++) {
   cals[i].addEventListener('click', function(e) {
       if (isClosed) {
           this.classList.add('h-strench-box-out');
           var content = this.querySelector('.h-strench-content');
           content.style.height = content.scrollHeight + 'px';
           isClosed = false;
       } else {
           if (this.classList.contains('h-strench-box-out')) {
               this.classList.remove('h-strench-box-out');

               // this.querySelector('.h-strench-content').style.height = '0';
               // This not working
               isClosed = true;
           } else {
               for (var j = 0; j < cals.length; j ++) {
               cals[j].classList.remove('h-strench-box-out');
               cals[j].querySelector('.h-strench-content').style.height = '0';
               // This not working
               }
           this.classList.add('h-strench-box-out');
           var content = this.querySelector('.h-strench-content');
           content.style.height = content.scrollHeight + 'px';
           }
        }
                        
    });
}

css

.h-strench-content {
    height: 0;
    padding: 0;
    display: none;
    overflow: hidden;
    transition: height 0.4s ease-in;
}
.h-strench-box-out .h-strench-content {
    display: block;
}
.h-strench-btn {
    transition: transform 0.3s ease-out;
}
.h-strench-btn::before {
    content: '\f13a';
    font-family: "Font Awesome 5 Free";
    font-size: 27px;
    font-weight: 600;
}

One more question. How can I change the height value(B) not element.style (A). Please compare the picture below. Please help thank you!

Answer 1

First step: make sure your querySelector calls are returning the correct elements. It will always return the first element that matches the selector.

As for the css: Height A is inline css, meaning it will always have priority over height B unless height B is marked !important . In order to revert to height B, height A must be removed entirely via remove property or simply set to null.

var obj = document.getElementById('name');
obj.style.removeProperty('height');
// if you want to return the old value...
// var oldValue = obj.style.removeProperty('height');

If you want to change contents in a stylesheet, see this example:

var declaration = document.styleSheets[0].rules[0].style;
var oldValue = declaration.removeProperty('height');

... However, be careful with the stylesheet example, as a change of indices can throw this off. It would be much safer to find an alternative that adds/removes classes with the values you desire instead.