Can I use CSS calc within Javascript?
There are some interesting things that happen when you use calc
with the same type of units, e.g. 10px + 5px
. It gets simplified to 15px
by the process that puts it onto the element.
So, to expand on rounin's great answer, here's some examples of that behaviour in action:
function growDiv(e) {
const thisDiv = e.target;
const x = 100;
const y = 42;
const z = 69;
let widthVal;
if (thisDiv.id == "simplifies") {
widthVal = `calc(${y + z}px + ${x}px + ${y}px)`;
} else if (thisDiv.id == "mixed-units") {
widthVal = `calc(0em + ${y + z}px + ${x * 2}px + ${y}px)`;
} else if (thisDiv.id == "variables") {
thisDiv.style.setProperty("--x", x + "px");
thisDiv.style.setProperty("--y", y + "px");
thisDiv.style.setProperty("--z", z + "px");
widthVal = "calc((var(--x) * 2) + var(--y) + (var(--z) * 2))";
}
thisDiv.style.width = widthVal;
thisDiv.innerHTML =
`input: ${widthVal}<br>style:${thisDiv.style.width}`;
}
document
.querySelectorAll("div")
.forEach((el) => el.addEventListener("click", growDiv, false));
.inner-div {
background-color: hotpink;
color: white;
font-weight: bold;
height: 100px;
margin-bottom: 5px;
text-align: center;
transition: all 0.5s linear;
width: 100px;
}
<div class="inner-div" id="simplifies">simplifies<br />1) Click Me</div>
<div class="inner-div" id="mixed-units">mixed-units<br />2) Click Me</div>
<div class="inner-div" id="variables">variables<br />3) Click Me</div>
Div 1 has all the same units, and therefore simplifies.
Div 2 has a token 0em
unit, which makes no difference to the calculation, but forces the full expression to come through.
Div 3 is my favourite because it's a little bit self-documenting. I do this because I'm a bit forgetful and it lets me see why I set that element to 728.3 high, not just that I did.
Yes, calc()
will work when setting styles in javascript.
Working Example:
var innerDiv = document.getElementsByClassName('inner-div')[0];
function growInnerDiv() {
innerDiv.style.setProperty('width', 'calc(100% + 224px)');
}
innerDiv.addEventListener('click', growInnerDiv, false);
.outer-div {
display: inline-block;
width: 200px;
height: 100px;
padding: 12px;
border: 1px solid rgb(255,0,0);
background-color: rgb(255,255,0);
}
.inner-div {
width: 100px;
height: 100px;
color: rgb(255, 255, 255);
font-weight: bold;
text-align: center;
line-height: 100px;
font-family: arial, helvetica, sans-serif;
background-color: rgb(255,0,0);
cursor: pointer;
transition: all 0.5s linear;
}
<div class="outer-div">
<div class="inner-div">Click Me</div>
<div>