A variation of the function provided by Paolo Bergantino that works directly on String:
String.prototype.addSlashes = function()
{
//no need to do (str+'') anymore because 'this' can only be a string
return this.replace(/[\\"']/g, '\\$&').replace(/\u0000/g, '\\0');
}
By adding the code above in your library you will be able to do:
var test = "hello single ' double \" and slash \\ yippie";
alert(test.addSlashes());
EDIT:
Following suggestions in the comments, whoever is concerned about conflicts amongst JavaScript libraries can add the following code:
if(!String.prototype.addSlashes)
{
String.prototype.addSlashes = function()...
}
else
alert("Warning: String.addSlashes has already been declared elsewhere.");