在 Javascript 中获取 Bootstrap 当前的主题颜色

Question

My objective is to create charts using chart.js using colors that match the current chosen Bootstrap 4 theme (there are multiple available for the site)

My current strategy is to have a badge of every color on the page:

  <div id="color-example-badge-primary" class="badge badge-primary" ></div >
  <div id="color-example-badge-warning" class="badge badge-warning" ></div >
  <div id="color-example-badge-danger" class="badge badge-danger" ></div >
  <div id="color-example-badge-secondary" class="badge badge-secondary" ></div >
  <div id="color-example-badge-light" class="badge badge-light" ></div >
  <div id="color-example-badge-success" class="badge badge-success" ></div >
  <div id="color-example-badge-info" class="badge badge-info" ></div >
  <div id="color-example-badge-dark" class="badge badge-dark" ></div >

and then use jQuery to pull the background colors into an array:

var themeColors = [$("#color-example-badge-primary").css('backgroundColor'),
                   $("#color-example-badge-warning").css('backgroundColor'),
                   $("#color-example-badge-danger").css('backgroundColor'),
                   $("#color-example-badge-secondary").css('backgroundColor'),
                   $("#color-example-badge-light").css('backgroundColor'),
                   $("#color-example-badge-success").css('backgroundColor'),
                   $("#color-example-badge-info").css('backgroundColor'),
                   $("#color-example-badge-dark").css('backgroundColor')
];

I can then give this array to chart.js to create a chart with the theme colors.

Is there a better way to get the current theme colors from the CSS using Javascript? Or is there no way without creating a DOM element and testing it's background color?

If there is an easy way to get CSS rules using Javascript without dealing with a DOM element, that'd be great.

Answer 1

Bootstrap stores its themed colors also inside CSS variables on the :root element.

A more appropriate way would be to extract these colors using getComputedStyle() and getPropertyValue('--variable')

 var style = getComputedStyle(document.body); var theme = {}; theme.primary = style.getPropertyValue('--primary'); theme.secondary = style.getPropertyValue('--secondary'); theme.success = style.getPropertyValue('--success'); theme.info = style.getPropertyValue('--info'); theme.warning = style.getPropertyValue('--warning'); theme.danger = style.getPropertyValue('--danger'); theme.light = style.getPropertyValue('--light'); theme.dark = style.getPropertyValue('--dark'); console.log(theme);

 <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js" integrity="sha384-ZMP7rVo3mIykV+2+9J3UJ46jBk0WLaUAdn689aCwoqbBJiSnjAK/l8WvCWPIPm49" crossorigin="anonymous"></script> <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js" integrity="sha384-ChfqqxuZUCnJSK3+MXmPNIyE6ZbWh2IMqE241rYiqJxyMiZ6OW/JmZQ5stwEULTy" crossorigin="anonymous"></script> <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css" integrity="sha384-MCw98/SFnGE8fJT3GXwEOngsV7Zt27NXFoaoApmYm81iuXoPkFOJwJ8ERdknLPMO" crossorigin="anonymous"> <div class="container"></div>

Now you can get these use these colors with JavaScript or jQuery as follow

element.style.backgroundColor = theme.primary; // Javascript
$(element).css('background-color', theme.primary); // jQuery

Answer 2

Use document.body.getElementsByTagName("*") to get all DOM in body and loop it to get what you want

 $(document).ready(function(){ var items = document.body.getElementsByTagName("*"); var arr=[]; for (var i = 4, len = items.length; i < len; i++) { arr.push(document.getElementById(items[i].id)!=null?$('#'+items[i].id).css('backgroundColor'):""); } console.log(arr) });

 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css"> <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script> <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script> <div id="color-example-badge-primary" class="badge badge-primary" >a</div > <div id="color-example-badge-warning" class="badge badge-warning" >a</div > <div id="color-example-badge-danger" class="badge badge-danger" >a</div > <div id="color-example-badge-secondary" class="badge badge-secondary" >a</div > <div id="color-example-badge-light" class="badge badge-light" >a</div > <div id="color-example-badge-success" class="badge badge-success" >a</div > <div id="color-example-badge-info" class="badge badge-info" >a</div > <div id="color-example-badge-dark" class="badge badge-dark" >a</div >