Iterators and Generators Back

1. Do not use iterators

• Do not use iterators. Prefer JavaScript's higher-order functions like map() and reduce() instead of loops like for-of.
• Eslint rules tags: no-interator

the reason is that this enforces(強制執行) our immutable(永恆不變的) rules. Dealing with pure functions that return values is easier to reason about than side-effects.

const numbers = [1, 2, 3, 4, 5];

/**
 * bad
 */
let sum = 0;
for (let num of numbers) {
    sum += num;
}

/**
 * good
 */
let sum = 0;
number.foreach(num => sum += num);

/**
 * best (use the funtional force)
 * arr.reduce(callback,[initialValue])
 * callback: function(previousValue, currentValue, index, array)
 * initialValue: the previousValue when first call the callback function
 */
const sum = numbers.reduce((total, num) => total += num, 0);

2. Do not use generators for now (reserved)

the reason is that generators cannot be transpiled well to ES5.