How to force inline html attribute in Svelte

Question

I want to use the browsers native support for resetting all fields' values of a form to their default or initial state using an <input type"reset"> element.

In HTML

In native HTML, clicking the reset input will remove any user input and reset the field to whatever is set in as the value inline parameter: value='default value', and if it's empty or missing, it will reset to an empty field.

input{
  display:block;
  margin:10px;
}

<form>
  <input type="text" value="default value">
  <input type="text" value="">
  <input type="text">
  <input type="reset">
  
</form>

In Svelte

In Svelte, the value attribute seems to never be printed in the html. As a results, clicking the reset input will empty every fields instead of reseting them to their initial values. Here's an example in Svelte REPL

So is there a way to force the native behaviour without handling it with javascript? is there a way to force svelte to print an inline attribute and never update it?

Answer 1

To my knowledge, Svelte doesn't have a built-in way to force setting the attribute instead of a property. If you look at the generated code in the REPL, it always sets the value property when value="something" is used.

You can force setting the attribute using a custom action.

function valueAttr(node, val) {
    node.setAttribute('value', val);

    return {
        update: function(val) {
            node.setAttribute('value', val);
        }
    }
}

See below for how the action can be applied to the input element. You will use this action instead of setting value="something" in the template. When the element is mounted, the function will run and set the value attribute on the element. The update function is optional, but will re-set the value attribute when the value passed to it changes.

<script>
    let dvalue = 'default value';
    
    function valueAttr(node, val) {
        // see definition above
    }
</script>
<form>
    <input type="text" use:valueAttr={dvalue}>
    <input type="text" use:valueAttr={"default value"}>
    <input type="text">
    <input type="reset">    
</form>

Updating your REPL code to use this action makes the reset input function correctly.