Delete or replace all pattern occurrences

delrepOccurrences.js

//delete all pattern occurrences 
String.prototype.deleteOccurrences = function (pattern) {
    return this.str.replace (RegExp(pattern,'gi'),"");
};

//replace all pattern occurrences 
String.prototype.replaceOccurrences = function (pattern, replace) {
    return this.str.replace (RegExp(pattern,'gi'),replace);
};

example:

console.log('11__22_33____44'.deleteOccurrences('_'));
//11223344