Using myvar==undefined (or any variable, which is undefined) is about 30% faster than typeof myvar=="undefined"
About window, I don't know if that would speed up accessing it but being a local variable it may be a bit faster. I think the main purpose is to allow some minifiers to replace local variables with a shorter one. On Jan 7, 2:17 pm, Jinpu Hu <huji...@gmail.com> wrote: > I see "var window = this" from latest svn code > > I use firebug debugger it. > > info:"Exception: redeclaration of const window" > > but in core.js > > var > // Will speed up references to window, and allows munging its name. > window = this, > // Will speed up references to undefined, and allows munging its > name. > undefined, > // Map over jQuery in case of overwrite > _jQuery = window.jQuery, > // Map over the $ in case of overwrite > _$ = window.$, > > i want to know what does "speed up references to window" mean?
