javascript - 我应该在哪里找到 indexOf 函数是如何为 JavaScript 核心编写的？

Question

我想看它，因为有一个算法面试问题问了类似的事情，但如果没有像 indexOf() 这样的内部函数，没有人能够解决它，除了要求不是使用内部函数来解决这个问题。既然我认为最好的实现已经存在，为什么我不直接向最好的实现学习呢？我想这就是他们如何为已经在 J​​avaScript 中的字符串编写 .indexOf()。

我的解决方案甚至展示它都让人感到羞辱...所以我决定不这样做，换句话说，有太多的条件切换比我想放在那里的要多。

谢谢

问题如下

Avoid using built-in functions to solve this challenge. Implement them yourself, since this is what you would be asked to do during a real interview.

Implement a function that takes two strings, s and x, as arguments and finds the first occurrence of the string x in s. The function should return an integer indicating the index in s of the first occurrence of x. If there are no occurrences of x in s, return -1.

Example

For s = "CodefightsIsAwesome" and x = "IA", the output should be strstr(s, x) = -1; For s = "CodefightsIsAwesome" and x = "IsA", the output should be strstr(s, x) = 10. Input/Output

[time limit] 4000ms (js) [input] string s

A string containing only uppercase or lowercase English letters.

Guaranteed constraints: 1 ≤ s.length ≤ 106.

[input] string x

String, containing only uppercase or lowercase English letters.

Guaranteed constraints: 1 ≤ x.length ≤ 106.

[output] integer

An integer indicating the index of the first occurrence of the string x in s, or -1 if s does not contain x

Bitw its from codefight https://codefights.com/interview-practice/task/C8Jdyk3ybixqQdAvM

对于任何有兴趣使用所有测试用例完整测试其代码的人，请点击此处(查看我的光标在图像 vvv 中指向的位置？)

https://codefights.com/interview-practice/topics/strings

Answer 1

no one was able to resolve it

我对这种情况感到有点震惊，因为它只是 2 个简单的嵌套 for 循环。例如，我花了不到几分钟的时间就完成了。

function strstr(a,b) {
  for (var o = 0; a[o]; o ++)
  {
    var found = true;
    for (var i = 0; b[i]; i ++) {
      if (a[o + i] !== b[i]) { found=false; break; }
    } 
    if (found) return o;
  }
  return -1;
}

var s = "CodefightsIsAwesome";
var x = "IA";

console.log(strstr(s, x));

s = "CodefightsIsAwesome";
x = "IsA";

console.log(strstr(s, x));