极客教程JavaScript 如何获取执行速度最快的函数在函数数组中的索引
在这个示例中，我们将学习如何在JavaScript中获取执行速度最快的函数在函数数组中的索引。
示例：
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： 解决问题需要遵循以下步骤：
- 首先，我们将遍历给定的数组。
- 我们将找出每个函数的执行时间，并将其存储在一个不同的数组中，与函数索引具有相同的索引值。可以通过使用 performance.now() 方法来计算执行时间。
- 最后，我们通过使用 Math.min() 方法来获取数组的最小值，打印出最小的索引。
示例1
在这个示例中，我们将计算每个函数执行所需的时间。然后，使用上述方法打印出最快函数的索引。
<script>
// 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);
</script>
输出：
"The hello function takes "
0.10000000009313226
"The hello1 function takes "
0
"The hello2 function takes "
0
"Index of fastest function:"
1
示例2
在此示例中，我们将计算函数执行某些数学运算所需的时间。然后，我们将打印出最快函数的索引。
<script>
// 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 = 0;
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);
</script>
输出：
Factorial of 4 is: 24
0.30000001192092896
6th fibonacci no is: 5
0.20000001788139343
Power 2 to 22 mod 1e9+7 is: 221047735
0.30000001192092896
Index of fastest function: 1