How to disable button from submitting form?

change the type from submit to button, so you don't need to preventDefault.

type="submit"

to

type="button"

Not directly related but you can also manage two submit buttons by using different name attributes on them. Then you can pick them up in PHP

if (Input::has('submit1'))
{
    // This was used - <button type="submit" name="submit1">Submit1</button>
}

if (Input::has('submit2'))
{
    // This was used - <button type="submit" name="submit2">Submit2</button>
}

As a side note, this might just be a typo from where you copied in your javascript, but you have

$("btnCombine")on("click",(function(event){ alert("w"); e.preventDeafult(); })

You use event as the argument in the callback, but then e.preventDefault(). One of those needs to be changed to match the other.

Just on a side note here as well. I faced the same issue on an input where I was using vuejs. Turns out in vue it is so simple it hurts... have a look:

my code that submits on enter:

<input
        ref="autocomplete"
        name="location"
        type="text"
        required="required"
        :class="classname"
        :id="id"
        :placeholder="placeholder"
        v-model="autocompleteText"
        @focus="onFocus()"
        @blur="onBlur()"
        @change="onChange"
        @keypress="onKeyPress"
     >

all I needed to do is change that line:

@keypress.enter.prevent="onKeyPress"

much better then that:

$("btnCombine")on("click",(function(event){ alert("w"); e.preventDeafult(); })

You can find reference here: https://vuejs.org/v2/guide/events.html