Settimeout() 不等待。 为什么？

Question

In upper part, both settimeout s inside "if" work properly. However settimeout s in lower part, the ones inside "else" does not wait. As far as I can see, I've written them in exact same style in both parts. What could be the reason ?

    elementCopy.addEventListener('mouseleave',()=>{
                    elementCopy.classList.add('leavin');
                    setTimeout(() => {                                         //  THESE WORK PROPERLY
                        elementCopy.style.width = '36vw';
                        setTimeout(() => {
                            elementCopy.parentElement.removeChild(elementCopy);
                        }, 400);         
                    }, 400);
                })
            }
            else{
                element.classList.add('card-active');
                element.addEventListener('mouseleave',()=>{
                    element.classList.add('leavin-mob');
                    
                    setTimeout(() => {                                         //  THESE DOESN'T
                        element.style.height = '38vh';
                        setTimeout(() => {
                        }, 400);
                    }, 400);
                })
            }

Answer 1

As one of the commenters noted, setTimeout is not a sleep kind of a method.

 setTimeout(() => {                                        
      element.style.height = '38vh';             
  }, 800);

Simply increase the timeout value if you need it later.

To explain this further, a nested setTimeout is rare unless you are doing something in the second timeout, the code itself as you have written works fine but it has nothing to execute - it's also set to 400ms which is a super small time. You can run the code below to see the second timeout works after 4 seconds.

setTimeout(() => {
  //  THESE DOESN'T
  console.log("This is 400ms!");
  //element.style.height = '38vh';
  setTimeout(() => {
    console.log(
      "This is 4 seconds but you usually would call something else here otherwise it has no effect or value"
    );
  }, 4000);
}, 400);