Iterator
Sequentially access the elements of a collection.
Provide a way to access the elements of an aggregate/collection object sequentially without exposing its underlying representation.
Most frequently used in Javascript.
The Iterator pattern allows clients to effectively loop over a collection of objects.
The Iterator pattern allows JavaScript developers to design looping constructs that are far more flexible and sophisticated.
EX:
var Iterator = function(items) {
this.index = 0;
this.items = items;
}
Iterator.prototype = {
first: function() {
this.reset();
return this.next();
},
next: function() {
return this.items[this.index++];
},
hasNext: function() {
return this.index <= this.items.length;
},
reset: function() {
this.index = 0;
},
each: function(callback) {
for (var item = this.first(); this.hasNext(); item = this.next()) {
callback(item);
}
}
}
function run() {
var items = ["one", 2, "circle", true, "Applepie"];
var iter = new Iterator(items);
// using for loop
for (var item = iter.first(); iter.hasNext(); item = iter.next()) {
console.log(item);
}
// using Iterator's each method
iter.each(function(item) {
console.log(item);
});
}
run();
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