url regex for ftp/http/https, can be without protocol name as well - using with contenteditable

urlRegex.js

var urlRegex = /^((?:ftp|http|https)?:\/\/)?((([a-z\d]([a-z\d-]*[a-z\d])*)\.)+[a-z]{2,}|((\d{1,3}\.){3}\d{1,3}))(\:\d+)?(\/[-a-z\d%_.~+]*)*(\?[;&a-z\d%_.~+=-]*)?(\#[-a-z\d_]*)?$/i;

/* the following will enforce appearance of 'www' while the protocol is optional, but if appears, must be correct */
urlRegex = /^((ftp|http|https)?:(\/\/)|(w{3}\.))((([a-z\d]([a-z\d-]*[a-z\d])*)\.)+[a-z]{2,}|((\d{1,3}\.){3}\d{1,3}))(\:\d+)?(\/[-a-z\d%_.~+]*)*(\?[;&a-z\d%_.~+=-]*)?(\#[-a-z\d_]*)?$/i;

/*check url on contenteditable element*/
var currentText,
$element = $("[contenteditable='true']");

var replaceAll = function (find, replace, str) {
    return str.replace(new RegExp(find, 'g'), replace);
};

// first replace all &npsp; chars with a regular space char 
currentText = replaceAll(String.fromCharCode(160)," ", currentText);

// then trim all spaces
currentText = $this.text().trim();

// do whatever

https://www.regex101.com/

The first regex above will accept: a.com | www.com | http://www.a.com