html - if display is block change it to none with javascript

Question

for this code

#element { 
  display : block
}

<div id="element"></div>

how can I write javascript code like

// button on click
if(element-display = block){
    // change it to display = none
}

Answer 1

style.backgroundColor = "red"

changeColor = function(){
  // Get the element by ID
  var div = document.getElementById("square");
  
  // Get the styles applied to that element
  var style = window.getComputedStyle(div)
  
  // Compare background color using rgb value
  if(style.backgroundColor == "rgb(0, 0, 255)")
    div.style.backgroundColor = "red";
}

#square{
  width: 50px;
  height: 50px;
  background-color: blue;
}

<div id="square"></div>
<button onclick="changeColor()">Change Color</button>