Rediscovering JavaScript: ES6, ES7 & ES8/

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Limitations: Generators, Exceptions, and Object Literals

Limitations: Generators, Exceptions, and Object Literals

Learn the limitations of arrow functions while creating generators, throwing exceptions, and returning object literals.

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Can’t be generators

In the Using generator in an infinite iteration section, we created a generator function that produced an infinite sequence of prime numbers. The code is repeated here for your convenience.

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'use strict';
//START:PRIMES
const primesStartingFrom = function*(start) {
  let index = start;
  
  while(true) {
    if(isPrime(index)) yield index;
    index++;
  }
};
//END:PRIMES

The primesStartingFrom variable refers to an anonymous function, which is marked with * to indicate it is a generator. Since the function is anonymous, you may be tempted to replace the anonymous function with an arrow function, like this:

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`use strict`;
//START:PRIMES
const primesStartingFrom = *(start) => { //Will not work
  //...
//END:PRIMES
  let index = start;
  
  while(true) {
    if(isPrime(index)) yield index;
    index++;
  }
}

The code will produce the following error:

const primesStartingFrom
...
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