JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container"> 
    <div class="child">1</div> 
    <div class="child">2</div> 
    <div class="child">3</div> 
</div>   
    
<button>задать :D</button>

CSS

div.container > .child { 
  width: 50px;
  border: 1px solid gray;
  float: left;
  margin-left: 5px;
}

JavaScript

$('button').click( function(e) { 
  $( 'div.container div.child' ).each( function(i) { 
      var w = $( this ).css( "width" );
      $( this ).css( "width", w );
  });
});