cannot return css property of HTML element [duplicate]

Answer 1

You can try this -

var  block = document.getElementById("block");
block.setAttribute("style","background-color: red;");

Answer 2

If you can use jQuery on your project I recommend using .css() jquery function

Eg.: Setting css

$('#block').css({background:'black'});

Getting css:

var cssValues = $('#block').css('background'});

See more about this here

Answer 3

You can use getComputedStyle:

var value = window.getComputedStyle(document.getElementById('block')).getPropertyValue("background-color");
console.log(value);

Answer 4

You could use single line of jQuery for this :

var value = $("#block").css("background-color");