你能帮我理解代码吗？任务是找到第一个非连续数

Question

const firstNonConsecutive = arr => arr.find((number, index) => index > 1 && number !== arr[index -1] + 1)

有没有人可以帮我分解上面的功能？我写了很长的代码来解决这个任务，有人给我发了一个更正，说我的代码可以简化。

Answer 1

我要做的第一件事就是添加大括号并将其分解为多行：

// This function takes an Array
const firstNonConsecutive = arr => {
  // And tries to find an item
  return arr.find((number, index) => {
    return index > 1 && // Starting from index 2 (the first 2 are ignored)
      number !== arr[index - 1] + 1; // Where the value is not (previous value + 1)
  });
}

console.log(firstNonConsecutive([128, 6, 2, 8])); // 2         -> ??
console.log(firstNonConsecutive([5, 6, 2, 8]));   // 2         -> correct
console.log(firstNonConsecutive([5, 6, 7, 8]));   // undefined -> correct

然后，如果您不知道该方法，您可以在某些时候查找有关 Array.prototype.find(). It takes a callback function which it will execute on every item until that callback returns true (or any ) 的一些文档。如果是，它将 return 该值。否则，如果没有项目符合条件，它将 return undefined.

这应该足以理解它的作用了吧？

奇怪的是它是从索引 2 (index > 1) 开始的。使用这个逻辑，这意味着永远不会检查第一个项目。也许那个条件应该是 index > 0:

// This function takes an Array
const firstNonConsecutive = arr => {
  // And tries to find an item
  return arr.find((number, index) => {
    return index > 0 && // Starting from index 1 (the first is ignored)
      number !== arr[index - 1] + 1; // Where the value is not (previous value + 1)
  });
}

console.log(firstNonConsecutive([128, 6, 2, 8])); // 6         -> correct
console.log(firstNonConsecutive([5, 6, 2, 8]));   // 2         -> correct
console.log(firstNonConsecutive([5, 6, 7, 8]));   // undefined -> correct

这里有一个更解构的方式来写这个：

function firstNonConsecutive(arr) {
  // Find an item that passes the condition
  return arr.find(passesCondition);
  
  function passesCondition(number, index) {
    return index > 0 && number !== arr[index - 1] + 1;
  }
}

console.log(firstNonConsecutive([128, 6, 2, 8])); // 6         -> correct
console.log(firstNonConsecutive([5, 6, 2, 8]));   // 2         -> correct
console.log(firstNonConsecutive([5, 6, 7, 8]));   // undefined -> correct

你能帮我理解代码吗？任务是找到第一个非连续数

Coud you help me understand the code ? the task is to find first non consecutive number

javascript

arrays

numbers

find

simplification