CSS calculates the parent width minus the total width of all previous elements

CSS Calculate the Width of an Element by Subtracting the Total Width of All Previous Elements

In front-end development, sometimes we need to calculate the width of an element by subtracting the total width of all previous elements. This is very useful in layout design, such as implementing a horizontally scrolling navigation bar or an element with adaptive width. In this article, we will explain how to achieve this using CSS.

1. Using Flex Layout

Flex layout is a powerful layout method that makes it easy to implement adaptive width elements. We can use the flex-grow property to control the width of an element, then calculate the width of the preceding element to subtract the total width of the preceding element.

<div class="container"> 
<div class="item">Item 1</div> 
<div class="item">Item 2</div> 
<div class="item">Item 3</div> 
</div> 

<style> 
.container { 
display: flex; 
} 

.item { 
flex: 1; 
background-color: lightblue; 
margin: 5px; 
} 
</style> 

In this example, we use flex layout to arrange three elements horizontally and divide their widths equally. If we want to subtract the total width of the preceding element, we can do so by setting the flex-grow property.

2. Using the calc() Function

Another way to calculate the width of an element is to use the CSS calc() function. We can use the calc() function to subtract the total width of the previous element.

<div class="container"> 
<div class="item" style="width: calc(100% - 100px);">Item 1</div> 
<div class="item" style="width: 50px;">Item 2</div> 
<div class="item" style="width: 100px;">Item 3</div> 
</div> 

<style> 
.container { 
display: flex; 
} 

.item { 
background-color: lightblue; 
margin: 5px; 
} 
</style> 

In this example, we use the calc() function to calculate the width of the first element as the parent element’s width minus 100px, thereby subtracting the total width of the preceding elements.

3. Calculate using JavaScript

If the above methods don’t meet your needs, you can also use JavaScript to calculate the element’s width. This is achieved by obtaining the width of the preceding element and then subtracting the total width of the existing elements.

<div class="container"> 
<div class="item" id="item1">Item 1</div> 
<div class="item" id="item2">Item 2</div> 
<div class="item" id="item3">Item 3</div> 
</div> 

<script> 
const item1 = document.getElementById('item1'); 
const item2 = document.getElementById('item2'); 
const item3 = document.getElementById('item3'); 

const totalWidth = item1.offsetWidth + item2.offsetWidth; 
item3.style.width = `calc(100% - ${totalWidth}px)`; 
</script> 

<style> 
.container { 
display: flex; 
} 

.item { 
background-color: lightblue; 
margin: 5px; 
} 
</style> 

In this example, we use JavaScript to retrieve the widths of the first two elements and then calculate the width of the third element as the parent element’s width minus the total width of the previous elements.

This method allows us to easily calculate the parent element’s width minus the total width of all previous elements. This is very useful in front-end development, helping us implement various complex layout designs.