11. Iterators | ES6 | JavaScript | TypeScript

11. Iterators | ES6 | JavaScript | TypeScript

• 1.
  Iterators | ES6 JAGADEESHPATTA ( PJ )
• 2.
  Agenda  Introduction Iterators Iterator on Array  Iterator on Set  Iterator on Object  Live Examples
• 3.
  Introduction  An objectis consider like an iterable when it has an implementation for Symbol.iterator property.  When an object contains Symbol.iterator implementation than the object allows us to use in for…of on it.  Array, Map, Set and String have their Symbol.iterator property already implemented.
• 4.
  Iterator on Array An array has its own iterator function implementation. Example var arr_one = [ 1, 2, 3, 4, 5 ]; for ( let element of arr_one){ console.log ( arr_one [ element ] ); }
• 5.
  Iterator on Set An set has its own iterator function implementation. Example var set_one = ( [ 1, 2, 3, 4, 5 ] ); for ( let element of set_one){ console.log ( set_one [ element ] ); }
• 6.
  Iterator on Object An object doesn’t have its own iterator function implementation. If we want to apply for…of on object we need to implement Symbol.iterator. Example var obj = { “name” : “PJ”, “designation” : “SSE” }
• 7.
  Iterator on Object(cont…) Custom Iterator obj [ Symbol.iterator ] = function( ) { let keys = Object.keys (obj), count = 0, isDone = false; let next = ( ) => { if ( count >= keys.length ) { isDone = true } return { done : isDone, value : obj [ keys [ count++ ] ] }; } return { next }; }
• 8.
  Iterator on Object(cont…) Custom Iterator for ( let property of obj ) { console.log ( obj [ property ] ); } // PJ, SSE
• 9.
  Any Q ?
• 10.
  Thank You