Toggle all <option>'s as checked/unchecked with the click of a <button>.

<select>
    <option></option>
    <option></option>
    <option></option>
</select>

<button></button>

jQuery("button").click(function(){
    jQuery("select :checkbox").each(function(){
        this.checked = !this.checked;
    });
});

Source: https://stackoverflow.com/questions/4177159/toggle-checkboxes-on-off

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Let's say you add an element to the DOM via jQuery:

$("<button class="delete">Delete</button>").appendTo("foo");

And want to later remove it via a jQuery event. Calling $('.delete').on('click') will not fire the event. This is because .on() only looks for elements that were loaded initially with the DOM. To resolve you can use …

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$( document ).ready(function() { });

is jQuery for:

document.addEventListener("DOMContentLoaded", function(event) { }); 

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$('#id').on('input', fuction(){
    var dInput = this.value;
    $('#output').text(dInput);
});

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