Characters that can break out of an inline style background-image url

<div id="test" style="background-image: url($[chr];width:100%">hello</div>

let myDiv = document.getElementById("test");0x0D
function getCSSProperty(element, property) {0x0D
            return window.getComputedStyle(element).getPropertyValue(property);0x0D
        }0x0D
const width = getCSSProperty(myDiv, 'width');0x0D
if (width === '100%') {0x0D
log(String.fromCharCode($[i]))0x0D
  }