resig_tricks.js

/* Funky JavaScript patterns from Resig's talk @ VanJS in Vancouver today. */
/* url: http://ejohn.org/apps/learn/bind.html */

/* loop => callback construct utilizing .call() for each member of the input array */
function loop(array, fn){
  for ( var i = 0; i < array.length; i++ ) {
    fn.call(array, array[i], i);
  }
}
var num = 0;
loop([0, 1, 2], function(value, i){
  assert(value == num++,
    "Make sure the contents are as we expect it.");
  assert(this instanceof Array,
    "The context should be the full array.");
});

/*
  potentially more convenient instantiation
  this way you never have to do x = new y();
*/
function User(first, last){ 
  if ( !(this instanceof User) ) 
    return new User(first, last); 
   
  this.name = first + " " + last; 
}
var u = User(); // <-- instance of user!!

/* pattern for co-ercing the arguments object into an array */
var x = function() {
  var args = Array.prototype.slice.call(args);
  
}

// pattern for or ( || ) operator comparison:
var something = foo || /* OR */ bar;
var something = false || 0; // FALSE
var something = false || 1; // 1!!
var something = -12 || 1; // -12 !!!!

/* for loop that calls a closure function with an argument from the loop. */
for ( var d = 0; d < 3; d++ ) (function(d){
 setTimeout(function(){
   log( "Value of d: ", d );
   assert( d == d, "Check the value of d." );
 }, d * 200);
})(d);

/* resig's assert function */
function assert(pass, msg){
  var type = pass ? "PASS" : "FAIL";
  jQuery("#results").append("<li class='" + type + "'><b>" + type + "</b> " + msg + "</li>");
}