π Iterator
iterator is function which has next function which returns object {done, value}
function genIterator(num) { return { next: function() { // β next!! return { done: true / false, // β done!! value: some value // β value!! } } } } For example??
function genIterator(num) { let i = 0 return { next: function() { return { done: false, value: i } } } } const it = genIterator() β How to use it ??
console.log(it.next()) // 0 console.log(it.next()) // 1 console.log(it.next()) // 2 console.log(it.next()) // 3 (By the way this is used basic style of closure)
β How to set max value?
function genIterator(num) { let i = 0 return { next: function() { if(i >= num) { return { done: true// β here!! } } else { return { done: false, value: i } } } } } const it = genIterator(10) let one = it.next() while(!one.done) { console.log(one.value) one = it.next() } // 0 1 2 3 4 5 6 7 8 9 π Generator
generator is function to create iterator
Actually it's just simple version of iterator π€π€
function* generator() { //β asterisk !! if(loop continue) { yield value; //β keyword "yield" } else { return value; } } function* β π€ what is this asterisk??
π it defines this function is GENERATOR !!!yield β π€ what is this??
π it returns {value, done}, like iterator
βΌ Let's make simple example
function* generator() { yield 1 yield 2 return 3 } const it = generator() // β return {value, done} like iterator !! console.log(it.next()) // {value: 1, done: false} console.log(it.next()) // {value: 2, done: false} console.log(it.next()) // {value: 3, done: true} console.log(it.next()) // {value: undefined, done: true} βΌ Let's transform counter function (genIterator function) by generator
function* genIterator(num = 10) { let i = 0 while(i < num) { yield i++ } } const it = genIterator(10) let one = it.next()// β execute by next() like itarator !!! while(!one.done) { console.log(one.value) one = it.next() } // 0 1 2 3 4 5 6 7 8 9 Generators are also iterable
function* alphabets() { yield 'a' yield 'b' yield 'c' } for(let letter of alphabets()) { console.log(letter) } // a b c 
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