Javascript-三元运算符-比较同一个函数两次？

Question

I have 3 variables top, mid, bot that I want to be logged depending on which part the div pops up (if topmost part of div , then top would be logged)

All you need to know is as the user scrolls down from the top of page, there are certain divs that we want to target. The 3 variables represent what needs to be logged whenever we hit a certain part of the div.

How would rewrite the console.log ternary operator to make sense, right now, the mid is not being run at all.

EDIT

trgt1 and trgt2 are 2 divs with the class ( .column ). trgt1 is the very first div that shows up, trgt2 should pop up as we scroll through halfway through the div.

CODE

function onScroll(event){

let top = "Column with id:`id-10` started to become visible on the page."
let mid = "Column with id:`id-50` is now more than 50% visible on the page."
let bot = "Column with id:`id-40` is now fully visible on the page."

targets.forEach(

    function(trgt,index){

          let isVisible = isScrolledIntoView(trgt);

          if (visibleStates[index] != isVisible)

          console.log(`Element index ${index} is now ${isVisible === trgt1 ? top : (isVisible === trgt2 ? mid : bot)}`);

          visibleStates[index] = isVisible;
        }
    );
}

Answer 1

You could work with a script that runs on scrolling the page. So add an eventlistener to the page.. Then you can debounce the scrolling, so control the amount of noise you allow on the window.. The function I have included is a working debounce function, just play with the wait in milliseconds. And then use your debounce function on the checkSlide() function where you put your running code in.

I know this is not a direct answer, it is another way of approaching the problem. This could work. If you want to do it your way, go for it..

Good luck!

window.addEventListener('scroll', debounce(checkSlide));

function checkSlide(){}

function debounce(func, wait=20, immediate = true){

var timeout; 

//debounce is a higher order function and will return another function 
return function run_code() {
    var context = this;

    //arguments is local variable of a function, refers to all arguments 
    var args = arguments; 

    //variable later is a function
    var later = function(){
        timeout = null;

        //if it is not time zero, apply checkSlide function 
        if(!immediate) func.apply(context, args);
    };

    var Callnow = immediate && !timeout;
    clearTimeout(timeout);
    timeout = setTimeout(later, wait);
    if(Callnow) func.apply(context, args);
}
}