Javascript Archives - Page 2 of 7

Javascript Local and Cookie Storage

Just a couple functions to make working with Local Storage and Cookies a little easier.

/**
  * SAVE any value to local storage
  * @param string Storage name
  * @param mixed Storage Value
  */
 function storeLocal(name, value){
	if (typeof(Storage) !== "undefined") {
		localStorage.setItem(name, JSON.stringify(value));
	}else{
		//if we do not have local storage for some reason try to use cookies
		//we are just saving for 1 day for now
		setCookie(name, JSON.stringify(value), 1);
	}
}

/**
 * GET any value to local storage
 * @param  string cname  Storage Name
 * @return string        Storage Value
 */
function getLocal(name){

if (typeof(Storage) !== "undefined") {
		return JSON.parse(localStorage.getItem(name));
	}else{
		//if we do not have local storage for some reason try to use cookies
		return JSON.parse(getCookie(name));
	}

}

/**
 * Set a Cookie
 * @param string cname  Cookie Name
 * @param mixed cvalue  Cookie Value
 * @param int exdays How many days before expire
 */
function setCookie(cname, cvalue, exdays) {
	var d = new Date();
	d.setTime(d.getTime() + (exdays*24*60*60*1000));
	var expires = "expires="+ d.toUTCString();
	document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";
}

/**
 * Get a cookie
 * @param  string cname  Cookie Name
 * @return string        Cookie Value
 */
function getCookie(cname) {
	var name = cname + "=";
	var ca = document.cookie.split(';');
	for(var i = 0; i <ca.length; i++) {
		var c = ca[i];
		while (c.charAt(0)==' ') {
			c = c.substring(1);
		}
		if (c.indexOf(name) == 0) {
			return c.substring(name.length,c.length);
		}
	}
	return "";
}

/**

* SAVE any value to local storage

* @param string Storage name

* @param mixed Storage Value

function storeLocal(name, value){

if (typeof(Storage) !== "undefined") {

localStorage.setItem(name, JSON.stringify(value));

}else{

//if we do not have local storage for some reason try to use cookies

//we are just saving for 1 day for now

setCookie(name, JSON.stringify(value), 1);

}

/**

* GET any value to local storage

* @param string cname Storage Name

* @return string Storage Value

function getLocal(name){

if (typeof(Storage) !== "undefined") {

return JSON.parse(localStorage.getItem(name));

}else{

//if we do not have local storage for some reason try to use cookies

return JSON.parse(getCookie(name));

}

/**

* Set a Cookie

* @param string cname Cookie Name

* @param mixed cvalue Cookie Value

* @param int exdays How many days before expire

function setCookie(cname, cvalue, exdays) {

var d = new Date();

d.setTime(d.getTime() + (exdays*24*60*60*1000));

var expires = "expires="+ d.toUTCString();

document.cookie = cname + "=" + cvalue + ";" + expires + ";path=/";

}

/**

* Get a cookie

* @param string cname Cookie Name

* @return string Cookie Value

function getCookie(cname) {

var name = cname + "=";

var ca = document.cookie.split(';');

for(var i = 0; i <ca.length; i++) {

var c = ca[i];

while (c.charAt(0)==' ') {

c = c.substring(1);

}

if (c.indexOf(name) == 0) {

return c.substring(name.length,c.length);

}

return "";

}

Javascript Sorting, Summing, and Rounding

I was running into an instance where I needed to be able to sort some arrays in either ASC or DESC order. I found some nice functions to help with that.

function jbSortDesc(a,b) {

return b - a;

}

function jbSortAsc(a,b) {

return a - b;

}

/**

* Round a number to X decimals

* @param Number value Any Number value

* @param int decimals The number of decimals to round to

* @return Number the resulting rounded number

function jbRound(value, decimals) {

var multiplier = Math.pow(10, decimals || 0);

return Math.round(value * multiplier) / multiplier;

}

/**

* Sum an array using the .reduce() function

function jbArraySum(total, num) {

return total + num;

}

Example Usage:

var arr = [6.1, 2.6 ,5.1, 2.5, 3.3, 5.4, 6.6];

//get the highest 6 elements of the array and sum them

var sum = arr.sort(jbSortDesc).slice(0, 6).reduce(jbArraySum)

//sum = 29.1

//in this case it is pointless, but you could see how this might be helpful

var roundedSum = jbRound(sum, 2);

//sum = 29.10

Calculate Age / Date Masking

Javascript is kind of wonky about their dates. Here is a simple function to calculate age based on a given date string.

function calculateAge(birthdate){

var today = new Date();

today = Date.parse(today);

var minutes = 1000 * 60;

var hours = minutes * 60;

var days = hours * 24;

var years = days * 365.25;

return Math.floor((today-birthdate) / years);

}

Note: This is not perfect and does not work with every possible date string, but it works pretty well with all standard US date formats.

Here is some decent code to setup some simple date masking.

$('.datemask').on('keydown', function(e){

if (e.key.length == 1 && isNaN(e.key)){

e.preventDefault();

return false;

}

if (e.key.length == 1){

var v = this.value;

if (v.match(/^\d{2}$/) !== null) {

if(v > 12) v = 12;

this.value = v + '/';

} else if (v.match(/^\d{2}\/\d{2}$/) !== null) {

v = v.split('/');

if(v[0]>12) v[0] = 12;

if(v[1]>31) v[1] = 31;

this.value = v[0] + '/' + v[1] + '/';

}else if (v.match(/^\d{2}\/\d{2}\/\d{4}$/) !== null) {

v = v.split('/');

if(v[0]>12) v[0] = 12;

if(v[1]>31) v[1] = 31;

var year = new Date().getFullYear();

var oldest = year - 150;

if(v[2]<oldest) v[2] = oldest;

if(v[2]>year) v[2] = parseInt(year)-1;

this.value = v[0] + '/' + v[1] + '/' + v[2];

}

return this.value;

}

});

Force Same Height on All Slick Slides

I love the slick slider, but sometimes the default functionality isn’t quite what I need. For a variety of other reasons the height of the slides can vary from slide to slide There is no built in “force height” option. Although it should be possible using “display: flex”, I try to avoid using flex on dynamic or complex elements that are hard to fail gracefully on.

I found some good code on the forums to force the slick slides to share the same height. I hope it helps you in the future too!

//when the slick slide initializes we want to set all of our slides to the same height

$('.slide-container').on('setPosition', function () {

jbResizeSlider();

});

//we need to maintain a set height when a resize event occurs.

//Some events will through a resize trigger: $(window).trigger('resize');

$(window).on('resize', function(e) {

jbResizeSlider();

});

//since multiple events can trigger a slider adjustment, we will control that adjustment here

function jbResizeSlider(){

$slickSlider = $('.slide-container');

$slickSlider.find('.slick-slide').height('auto');

var slickTrack = $slickSlider.find('.slick-track');

var slickTrackHeight = $(slickTrack).height();

$slickSlider.find('.slick-slide').css('height', slickTrackHeight + 'px');

}

Quick Javascript Date Format

Format pretty much any valid date and return it in the standard Y-m-d format.

function formatDate(date) {

var d = new Date(date),

month = '' + (d.getMonth() + 1),

day = '' + d.getDate(),

year = d.getFullYear();

if (month.length < 2) month = '0' + month;

if (day.length < 2) day = '0' + day;

return [year, month, day].join('-');

}

Basic Template Engine

Sometimes I need to setup Javascript templating for a page or two, or even just a form. I found a cool solution over on Krasimir Tsonev’s blog. I thought I would save it here for future use.

Template

I don’t really like having to setup long strings in javascript, it is just so ugly. So I use the <script type=”text/template”> approach to separate out my templates from my code. Here is an example.

<div class="form-group">
			<label>Last Name(s):</label>
			<input type="text" maxlength="100" name="attendee[<%dataID%>][lastname]" class="form-control req" value=""/>
		</div>

<div class="form-group">
			<label>Phone:</label>
			<input type="text" maxlength="20" name="attendee[<%dataID%>][phone]" class="form-control req phone-input inline-block" value="" />
		</div>

<div class="form-group">
			<label>Email:</label>
			<input type="email" maxlength="100" name="attendee[<%dataID%>][email]" class="form-control req validate-email" value="" />
		</div>

<div class="form-group">
			<label>Ticket: <span class="ticket_price">$<%ticketPrice%></span></label>
		</div>

</div>
</script>

<h5>Attendee #<%dataID%> Information:</h5>

<label>First Name(s):</label>

<input type="text" maxlength="100" name="attendee[<%dataID%>][firstname]" class="form-control req" value="" />

</div>

<input type="text" maxlength="100" name="attendee[<%dataID%>][lastname]" class="form-control req" value=""/>

</div>

<label>Phone:</label>

<input type="text" maxlength="20" name="attendee[<%dataID%>][phone]" class="form-control req phone-input inline-block" value="" />

</div>

<label>Email:</label>

<input type="email" maxlength="100" name="attendee[<%dataID%>][email]" class="form-control req validate-email" value="" />

</div>

<label>Ticket: <span class="ticket_price">$<%ticketPrice%></span></label>

</div>

</script>

This is just a basic “Attendee” template for some event. Notice the <%stuff%> inside there. That is where the magic happens.

Template Engine

Here is where the real magic happens.

function TemplateEngine(tpl, data) {

var re = /<%([^%>]+)?%>/g, match;

while(match = re.exec(tpl)) {

tpl = tpl.replace(match[0], data[match[1]])

}

return tpl;

}

//Usage

var attendeeTemplate = $('#attendee-tempate').html();

var newAttendee = TemplateEngine(attendeeTemplate, {

dataID: $('.attendee').length + 1,

ticketPrice: 50

})

So as you can see the “TemplateEngine” just takes some input and replaces anything between the <% %> symbols. Krasimir actually has a more functional version setup on his blog as well with support for some logic, but that is more than I needed. And if I ever did need that much functionality I would just turn to a full Template Engine.

Update:

I noticed a strange flaw in this template engine when working with templates that require multiple replacements on the same line of text. Here is another version of the template engine you can use which should find all variables in your template, regardless of how many are on a line.

function TemplateEngine(tpl, data) {

for(var key in data){

var re = new RegExp("<%" + key + "%>", "gi");

tpl = tpl.replace(re, data[key]);

}

return tpl;

}