javascript - javascript中&&的运算符优先级/执行顺序是什么

Question

javascript 中 && 的运算符优先级/执行顺序是什么

str = "string"
iterator = str[Symbol.iterator]()
while ( result = iterator.next() && !result.done ) { // Error result is not defined..Is it not a left to right evaluatation
  console.log( result.value )
}

通过添加括号来更改它似乎可以解决问题......

str = "string"
iterator = str[Symbol.iterator]()
while ( ( result = iterator.next() ) && !result.done ) { // Parenthesis seem to take precedence
  console.log( result.value )
}

Answer 1

嗯，因为你有赋值，所以它被执行为:

result = (iterator.next() && !result.done)

代替

(result = iterator.next()) && !result.done

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence