Javascript 记住 combobox 值

Question

I currently have 3 combo boxes containing values which apply styles to the page using javascript.

All these styles are applied to a cookie and read on body load, however I'd like to also set the combo box's values to match the applied styles.

How do I go about setting a combo box value based on a cookie or applied style?

<select name="sizes" onchange="fontSize(accessibility.sizes.value);"> 
  <option value='-1'>Select</option>
  <option value='10'>Small</option> <option value='12.75'>Medium</option>
  <option value='15.5'>Large</option>
</select>

function fontSize(textSize) { 
  var element = document.getElementById('content'); 
  if (element) {
   element.style.fontSize = textSize + 'px'; 
   createCookie("Font Size", textSize, 365);   
  }
} 

Thanks in advance!

Answer 1

If changing the select is changing the style, first select the relevant value then trigger the onchange. Notice I changed your script to save the selectedIndex and to apply the change after I set the index. Also please notice I pass (this) which the the select object itself and I have added an ID to it. Lastly I put the medium fontsize as the first item in case people want to reset. Please change that to whatever is the default font size

window.onload=function() {
  var sel = document.getElementById('sizes');// get the select with ID=sizes
 // the following statement gets the select and sets the index to the cookie content if
 // there IS a cookie, else it sets it to 0
 var idx = getCookie("FontSizeIdx") || 0;
  sel.selectedIndex = parseInt(idx,10); // make sure it is a number
 // now call the function and pass the select to it
  fontSize(sel);
}
function fontSize(sel) { // select object is passed as (this) and ends up here as (sel)
  var textSize = sel.options[sel.selectedIndex].value; // get the value
  var element = document.getElementById('content'); // get the content object
  if(element) { // does it exist?
    element.style.fontSize = textSize + 'px'; // set the font size 
    createCookie("FontSizeIdx", sel.selectedIndex, 365); // save the index
  }
} 

<select name="sizes" id="sizes" onchange="fontSize(this);"> 
<option value='12.75'>Select (default is medium)</option> 
<option value='10'>Small</option> 
<option value='12.75'>Medium</option> 
<option value='15.5'>Large</option> 
</select>