Get width of an element and apply to another relative to the first one?

- 1 answer


I have a dropdown menu, and I'm trying to get the submenus to be the same width as the top level page.

My HTML is structured like something this (This is for a wordpress theme, so I have very little control over the document structure):

<ul class="menu">
    <li class="menu-item-has-children menu-item">
        <a>Top Level Page 1</a>
        <ul class="submenu">
            <li class="menu-item-has-children menu-item">Sub Page 1</li>
            <li>Sub Page 2</li>
            <li>Sub Page 3</li>
    <li class="menu-item-has-children menu-item">
        <a>Top Level Page 2 which has a different width</a>
        <ul class="submenu">
            <li>Sub Page 4</li>
            <li>Sub Page 5</li>
            <li>Sub Page 6</li>

I first turned to CSS: li ul {
    width: 100%;

... but that makes it the width of the for some reason. I also tried putting the "width: 100%" in other places, but no such luck.

I decided to turn to jquery, inspired by this post. I tried this initially:

$(' li ul').width($( li).width());

...but it just sets all the submenus to the width of the first li, ignoring parenting relationships.

I've tried each of the following to select just the parent (or the sibling a, in case that's what's determining the width) of that particular ul, but none of them seem to work:

$(' li ul').width($(this).parent('li').width());

$(' li ul').width($(this).parent().width());

$(' li ul').width($(this).parent('li').children('a').width());

$(' li ul').width($(this).siblings('a').width());

Can you not use $this in this context? If so, what would be a better way to accomplish what I'm trying to do?




you're overthinking this:

   width: 20vw; //view width 
   position: relative;

    position: absolute;
    left: 0;
    width: 20vw;

Assuming you haven't defined any child elements of .menu as relative or absolute this will align the submenu to the left hand side of .menu and obviously the widths are defined as the same.


Use google chrome inspector to see what css rules are being applied to the elements but a couple of examples of what can be done with css.

Natural flow (submenu is a block item and will fill parents width

or defined rules

Now for the jQuery version:

Before explaining this you should note:

  1. jQuery needs to be included on the frontend - this is a lot of code for changing css values, this takes time for the user to download and use

    1. when working with jQuery you need to wait for the library to load before attempting to use (hence doc. ready in example). This will probably mean on slower connections that a user will see the change happening.
    2. WP expects the word jQuery as a call rather than $ which will generate a error (check your console)

      //return a list of dom items that match the selector
      //each ilterates over the list
          jQuery('.menu > li').each(function(){
              //this refers to the current element in the list we are working with
              var wt= jQuery(this).width();
              //search within this element for the element we want and set width