Useful Javascript
Published May 14, 2012
Web tricks - Useful Javascript
Here we will see some small JavaScript functions that may be quite useful.
Log a message
Who, among those ever developped in a programming language, never used a printf or some awful method to debug their code? I thought so… Indeed, it is bad, but you must admit that it is quite easy and simple to use. If you agree with me, you should like the following function:
/**
* Simple function to log a message.
*
* If there is no console, this function will display the message in an alert
* box.
*
* @param message Message to log.
*/
function log(message) {
if (typeof console !== 'undefined')
console.log(message);
else
alert(message);
}
I wish to thank Loïc Yon for giving me this quite sympathic function 
.
Redirect the user
It is quite frequent to encounter a «temporary» webpage that will redirect you to another page after a few seconds. Well, here is how to proceed through JavaScript:
/**
* Function to redirect the browser.
*
* If no redirection URL is passed, the function will simply reload the current page.
*
* @param redirection URL for redirection.
* @param delay (Optional) Delay in milliseconds before redirection.
*/
function redirect(redirection, delay) {
if (redirection != null) {
if (delay != null)
setTimeout("window.document.location = '"+redirection+"'", delay);
else
window.document.location = redirection;
}
else
window.document.reload();
}
Managing Strings
We use strings everywhere in programming language, and JavaScript is no exception to it. However, functions to manage strings, like trimming it or testing prefix/suffix, were not always present on all browsers.
If you are concerned about cross browsers/versions compatibility, you can always use the following functions:
/**
* Function to test if a string ends with another string or not.
*
* @see <a href="http://stackoverflow.com/questions/280634/endswith-in-javascript" *="">StackOverflow: endsWith in javascript</a>
*
* @param str String to test.
* @param suffix Suffix to test if present at the end.
* @return true if str ends with suffix, false if not.
*/
function strEndsWith(str, suffix) {
return typeof str.endsWith !== 'undefined' ? str.endsWith(suffix) : str.indexOf(suffix, str.length - suffix.length) !== -1;
}
/**
* Function to test if a string starts with another string or not.
*
* @param str String to test.
* @param prefix Prefix to test if present at the start.
* @return true if str starts with prefix, false if not.
*/
function strStartsWith(str, prefix) {
return typeof str.startsWith !== 'undefined' ? str.startsWith(prefix) : str.indexOf(prefix, 0) == 0;
}
/**
* Function to test if a string starts with another string or not.
*
* @param str String to test.
* @param prefix Prefix to test if present at the start.
* @return true if str starts with prefix, false if not.
*/
function strTrim(str) {
return typeof str.trim !== 'undefined' ? str.trim() : str.replace(/^\s+|\s+$/g, '');
}