How to check if the element is not the first-child?

How do you know if the current element is not the first-child?

It should work with $(this), for example:

$("li").click开发者_开发技巧(function(e) {
    if (/* $(this) is not the first-child */)
    {
        /* do something */
    }
});

You can do this just to test an element if it's the first child: $(this).is(':first-child'). Other selectors like :last-child would work too.

You could simply ask for its .index() position (relative to its siblings).

$(this).index();   // returns a zero based index position

For all li's in #thing that aren't first child:

$('#thing li:not(:first-child)')

see http://api.jquery.com/not-selector/

If you would like to select everything except the first child, this is how to do it:

$('#some-parent').children().not(':first')

Also, you can check if $(this).prev().length is defined, like in:

if (!$(this).prev().length){ //This means $(this is the first child
    //do stuff
}

Check the index

$(this).index() == 0 // is first

Keep it simple, use the DOM

$("li").click(function(e) {

    if (this.previousSibling != null)
    {
        /* do something */
    }

});

For people who want a vanilla JS solution:

<div id="parent">
  <div id="child-1"></div>
  <div id="child-2"></div>
  <div id="child-3"></div>
</div>

let element = document.getElementById('child-1');
console.log(element.parentElement.firstElementChild === element); // true
console.log(element.parentElement.lastElementChild === element);  // false

element = document.getElementById('child-2');
console.log(element.parentElement.firstElementChild === element); // false
console.log(element.parentElement.lastElementChild === element);  // false

element = document.getElementById('child-3');
console.log(element.parentElement.firstElementChild === element); // false
console.log(element.parentElement.lastElementChild === element);  // true

It's not the most elegant thing but it gets the job done.

You can even check if it's the nth element in the same fashion.

let n = 2; // check if it's the 2nd child

let element = document.getElementById('child-2');
// index starts at 0
console.log(element.parentElement.children[-1 + n] === element); // true

jQuery .not()

$(this).not(':first');

$("li").click(function(e) {
   if ($(this).index != 0 )
  {
      /* do something */
   }
});

A less complex (IE 9 compatible) pure/vanilla JavaScript way to achieve this is to use the matches function of Element. See https://developer.mozilla.org/en-US/docs/Web/API/Element/matches

Example:

console.log( document.querySelectoer( '#my-div' ).matches( ':first-child' ) ); // true or false