Unfortunately it wasn't there from day one. It was only specified a year or two ago (thus IE 8 and Opera 11.50 didn't have it, and apparently Safari 5.1 still d

Unfortunately it wasn't there from day one. It was only specified a year or two ago (thus IE 8 and Opera 11.50 didn't have it, and apparently Safari 5.1 still doesn't) so you have to be prepared to check for it and roll your own. http://kangax.github.com/es5-compat-table/ http://kangax.github.com/es5-compat-table/