how create method twice? can't understand how change in body of function. why doesn't work?
function twice() { var buf = []; ( var = 0; < this.length; i++ ) { buf.push(this[i]); } ( var = 0; < this.length; i++ ) { buf.push(this[i]); } = buf; } array.prototype.twice = twice; = [1,2,3]; a.twice(); a; // [1,2,3,1,2,3]
i can't understand how change in body of function
if mean value of this, can't. don't have you're doing
you're close, have fair bit remove:
function twice() { var i, l; (l = this.length, = 0; < l; ++i) { this.push(this[i]); } } remember, array object. change contents, change contents, don't have change reference it.
note, though, can use trick on modern browser:
function twice() { this.push.apply(this, this); } that works using function#apply function, calls function call on (so, push in our case) using first argument give object operate on, , second argument arguments pass function (which takes array). more on mdn , in spec. happens push allows pass arbitrary number of arguments, , push each 1 in order. if you're trying add contents of array array second time, 1 line (on modern browsers, older ie implementations don't use of push.apply).
