{"id":423,"date":"2023-07-23T02:16:42","date_gmt":"2023-07-23T02:16:42","guid":{"rendered":"https:\/\/nikspace.co.in\/?p=423"},"modified":"2023-07-23T02:18:59","modified_gmt":"2023-07-23T02:18:59","slug":"javascript-generator","status":"publish","type":"post","link":"https:\/\/nikspace.co.in\/?p=423","title":{"rendered":"JavaScript generator"},"content":{"rendered":"\n

The feature I will be discussing in this post is generators. This is a new feature that was introduced in ES6.
A generator is a function that can be stopped midway and start off from where it left. This is very different from a normal function which runs to completion and if started again will start from the beginning.
Let\u2019s look at a normal function for generating Fibonacci numbers for n terms:<\/p>\n\n\n\n

      \/\/ program to generate fibonacci series up to n terms\n      \/\/ take input from the user\n      const number = parseInt(prompt(\"Enter the number of terms: \"));\n\n      console.log(\"Fibonacci Series:\");\n      for (i of fibonacci(number))\n      {\n        console.log(i);\n      }\n\n      function fibonacci(nums)\n      {\n        let fib = [0, 1];\n        let data = [];\n\n        for(let i = 2; i <= nums; i++)\n        {\n          fib[i]=fib[i - 1] + fib[i - 2];\n          data.push(fib[i]);\n        }\n        return data;\n      }<\/code><\/pre>\n\n\n\n
Code pen link – https:\/\/codepen.io\/ragesh_d\/pen\/yLzNQPG<\/a><\/p>\n\n\n\n
This is how you would create one using generators:<\/p>\n\n\n\n
 \/\/ Fibonacci generator\n      function* fibonacci()\n      {\n        [a, b] = [0, 1]\n        while (true)\n        {\n          yield a;\n          [a, b] = [b, a + b]\n        }\n      }\n      \/\/ Instantiates the fibonacci generator\n      var fib = fibonacci();\n      const number = parseInt(prompt('Enter the number of terms: '));\n      \/\/ gets first n numbers from the Fibonacci generator starting from 0\n      for (let i = 0; i < number; i++)\n      {\n        console.log(fib.next().value);\n      }<\/code><\/pre>\n\n\n\n
Code pen link – https:\/\/codepen.io\/ragesh_d\/pen\/dyVoQdp<\/a><\/p>\n\n\n\n
The advantage of the generator method is that the calling program does not get back a list but just the next value, this means that it does not need to store the whole list so space wise it\u2019s a much more efficient approach.
Now let\u2019s see the syntax to creating a generator function, as can be seen from the example the function* is used to differentiate a generator from a normal function. It also uses a yield which is like a return but the function will halt after returning until the calling function invokes it using a next().
Let\u2019s go over some advantages of generators:<\/p>\n\n\n\n