如何在 JavaScript 中执行速度最快的函数数组中获取函数的索引？

在这个例子中，我们将学习如何在 JavaScript 中执行速度最快的函数数组中获取函数的索引。

例子：

Input: fun[] = [ hello, hello1, hello2 ]
Output: index of fastest is 0.

Explanation: Function hello execute fastest in all functions.

Input: fun[] = [ while1, while2, while3 ]
Output: index of fastest function is 2 

方法：必须遵循以下步骤来解决问题：

• 我们将首先遍历给定的数组。
• 我们将找到每个函数所花费的时间并将其存储在具有与函数索引相同的索引值的不同数组中。可以通过使用performance.now()方法获取时间差来找到所花费的时间。
• 最后，我们通过使用Math.min()方法获取数组的最小值来打印最小索引。

下面的示例演示了这种方法。

示例 1：

Javascript

  // 1st function
  function hello() {
    var s = "";
    var ans = ["The", " hello function ", "takes "];
    for (var i = 0; i < 3; i++) s += ans[i];
    console.log(s);
  }
 
  // 2nd function
  function hello1() {
    var s = "";
    var ans = ["The hello1 function", " takes "];
    for (var i = 0; i < 2; i++) s += ans[i];
    console.log(s);
  }
 
  // 3rd function
  function hello2() {
    var ans = "The hello2 function takes ";
    for (var i = 0; i < 1; i++) console.log(ans);
  }
 
  // Function to check time required by each function
  function findTime(f) {
 
    // Storing initial time in start
    var start = performance.now();
 
    // Calling the function
    f();
 
    // Storing time after running the function
    var end = performance.now();
 
    // Return time taken by function
    return end - start;
  }
 
  function findMinTime() {
 
    // Initializing array of functions
    var fun = [hello, hello1, hello2];
 
    // Initialising array of time taken by function
    var ans = [];
 
    // Iterating over all the functions and
    // storing time taken by them
    for (var i = 0; i < 3; i++) {
      var n = findTime(fun[i]);
      ans[i] = n;
      console.log(ans[i]);
    }
 
    // Finding the minimum time in array
    var answer = Math.min.apply(null, ans);
    c = ans.indexOf(answer);
 
    // Return index of fastest array
    return c;
  }
 
  var minTime = findMinTime();
  console.log("Index of fastest function:", minTime);

输出：

The hello function takes
5.8547000009566545
The hello1 function takes
0.2459999993443489
The hello2 function takes
0.19830000028014183
Index of fastest function
2

示例 2：

Javascript

  // 1st function
  function fac(n) {
    let fact = 1;
    for (let i = 1; i < 4; i++)
      fact *= i;
    console.log("Factorial of 4 is:", fact);
  }
 
  // 2nd function
  function fibo() {
    let fab = 1;
    let j = 1;
    for (let i = 2; i < 6; i++) {
      let temp = fab;
      fab += j;
      j = temp;
    }
    console.log("6th fibonacci no is:", fab);
  }
 
  // 3rd function
  function binpow() {
    let j = 2;
    let k = 22;
    for (let i = 0; i < k; i++)
      j = ((j * j) % 1e9) + 7;
    console.log(
      "Power 2 to 22 mod 1e9+7 is:", j
    );
  }
 
  // Function to check time required
  // by each function
  function findTime(f) {
 
    // Storing initial time in start
    var start = performance.now();
 
    // Calling the function
    f();
 
    // Storing time after running the function
    var end = performance.now();
 
    // Return time taken by function
    return end - start;
  }
 
  function findMinTime() {
 
    // Initializing array of functions
    var fun = [fac, fibo, binpow];
 
    // Initialising array of time
    // taken by function
    var ans = [];
 
    // Iterating over all the functions
    // and storing time taken by them
    for (var i = 0; i < 3; i++) {
      var n = findTime(fun[i]);
      ans[i] = n;
      console.log(ans[i]);
    }
 
    // Finding the minimum time in array
    var answer = Math.min.apply(null, ans);
    c = ans.indexOf(answer);
 
    // Return index of fastest array
    return c;
  }
 
  var minTime = findMinTime();
  console.log("Index of fastest function:",
              minTime);

输出：

Factorial of 4 is: 6
7.554999999701977
6th fibonacci no is: 8
0.22690000012516975
Power 2 to 22 mod 1e9+7 is: 221047735
0.25120000168681145
Index of fastest function: 1