Using Javascript to display weights

I have a javascript function that changes a user preference, if they want weights to be metric or in imperial.

On my page I print out the weight, IE:

This is some description:

This product weights <b>200 KG</b>

Blah blah

I need to make it so that Javascript changes the weight measurement for all weights on the page, and am not sure the best way to tackle this. Can you create your own tags, or tag properties?

Thank开发者_StackOverflow社区s for any suggestions, JQuery is fine.

I'd recommend using strong rather than b, but the below will work for either of them.

Edit: Better solution than using a class, with working example, below.

Tag the weights with a class, e.g.:

This product weighs <strong class='weight'>200 KG</strong>

$('.weight').each(function() {
    var $this = $(this);
    var original = $this.text();
    var converted = /* ...convert the weight here... */;
    $this.text(converted);
});

Obviously you can condense that a bit, kept it verbose for clarity.

Better solution:

Tag the elements with the original weight (the one you store in your database) as a data-weight attribute, e.g.:

This product weighs <strong data-weight='200'>200 KG</strong>

Then convert from that value:

$('[data-weight]').each(function() {
    var $this = $(this);
    var value = $this.attr("data-weight");
    if (usingMetric) {
        $this.text(value + " KG");
    }
    else {
        value = parseFloat(value) * 2.20462262; // Convert to imperial
        $this.text(value.toFixed(2) + " lbs");
    }
});

Working example: http://jsbin.com/icure3

Attributes in the form data-xyz will pass validation as of HTML5; prior to HTML5 they are technically invalid, but harmless. But if you prefer a version that doesn't use data-weight, you can do it with classes instead: http://jsbin.com/icure3/2 (inspired by Reigel's answer to Tom's other question).

If you see a delay when switching between metric and imperial on slower browsers (I'm looking at you, Microsoft), you can help jQuery's selector engine optimize by giving it more context than just "[data-weight]". jQuery's engine supports nearly all of CSS3. For instance, if you always use the data-weight attribute only one one kind of tag (say, strong tags), change the selector to "strong[data-weight]" so the selector engine knows it can optimize for just one specific tag name. Similarly, if all of these are inside some container (e.g., a div with the ID "productList" for instance), you can help the engine out even more ("#productList strong[data-weight]") so it can ignore anything outside that div. I've kept it completely general above. But probably only bother if the page is big and complex enough that you see a performance issue.

Final thought: To throw a bone to browsers with JavaScript disabled, you might include both values in a title attribute as well, e.g.:

This product weighs <strong title='200 KG / 441 lbs' data-weight='200'>200 KG</strong>

...so it shows up as a tooltip on browsers that do that. I included that in the example above.

I would add a class .weight and use this to target all the weights..

$('.weight').each(function(){...})

If you want to change the innerHTML you can use the html() method directly

$('.weight').html(function(idx, oldhtml){
 // you can use the oldhtml to extract info and create the new text here..
  $(this).html( ../*you new html here*/.. ); // replace existing with new html ..
})

HTML:

<b class="weight">200 KG</b>

Javascript:

$("#UnitChangeButton").click(function() {
  $('.weight').each(function(){
    txt = $(this).text();
    newTxt = convert(txt);
    $(this).text(newTxt);
  });
});

You need to implement the convert function. You can store the state (metric or imperial) in a javascript variable.