Some Useful JavaScript & jQuery Snippets – Part 2

Development January 7, 2010 by cody 25 Comments

snippets_part2

  • Check if cookies are enabled
    • $(document).ready(function() {
    var dt = new Date();
    dt.setSeconds(dt.getSeconds() + 60);
    document.cookie = "cookietest=1; expires=" + dt.toGMTString();
    var cookiesEnabled = document.cookie.indexOf("cookietest=") != -1;
    if(!cookiesEnabled){
        //cookies are not enabled
    }
});
  • Toggle all checkboxes
    • var tog = false; // or true if they are checked on load
$('a').click(function() {
    $("input[type=checkbox]").attr("checked",!tog);
    tog = !tog;
});
  • Get the index of an element
    • $("ul > li").click(function () {
    var index = $(this).prevAll().length;
});
  • Validate date of birth
    • $("#lda-form").submit(function(){
    var day = $("#day").val();
    var month = $("#month").val();
    var year = $("#year").val();
    var age = 18;
    var mydate = new Date();
    mydate.setFullYear(year, month-1, day);

    var currdate = new Date();
    currdate.setFullYear(currdate.getFullYear() - age);
    if ((currdate - mydate) < 0){
        alert("Sorry, only persons over the age of " + age + " may enter this site");
        return false;
    }
    return true;
});
  • Test if an element is visible
    • if($(element).is(":visible")) {
    //The element is Visible
}
  • Counting child elements
    • <div id="foo">
<div id="bar"></div>
<div id="baz">
<div id="biz">
</div>
<span><span>
</div>

//jQuery code to count child elements
$("#foo > div").length
  • Center an element on the screen
    • jQuery.fn.center = function () {
    this.css("position","absolute");
    this.css("top", ( $(window).height() - this.height() ) / 2+$(window).scrollTop() + "px");
    this.css("left", ( $(window).width() - this.width() ) / 2+$(window).scrollLeft() + "px");
    return this;
}

//Use the above function as:
$(element).center();
  • Moving options from list A to list B
    • $().ready(function() {
    $('#add').click(function() {
        !$('#select1 option:selected').appendTo('#select2');
    });
    $('#remove').click(function() {
        !$('#select2 option:selected').appendTo('#select1');
    });
});
  • Select all checkboxes
    • $(document).ready(function(){
    $("#checkboxall").change(function(){
        var checked_status = this.checked;
        $("input[name=checkall]").attr("checked", checked_status);
    });

});
  • Get the current URL
    • $(document).ready(function() {
    var pathname = window.location.pathname;
});
  • Check if and which key was pressed
    • $(function() {
    $(document).keypress(function(e){
        switch(e.which){
        // "ENTER"
        case 13:
        alert('enter pressed');
        break;

        // "s"
        case 115:
        alert('s pressed');
        break;

        (...)

        }
    });

});

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