使用javascript Array reduce()方法有什么实际的好处吗？
使用javascript Array reduce()方法有什么实际的好处吗？
提问于 2012-03-09 13:36:52
reduce()方法的大多数用例都可以很容易地用for循环重写。在JSPerf上的测试表明，reduce()通常要慢60%-75%，这取决于每次迭代中执行的操作。
那么，除了能够以“函数式风格”编写代码之外，使用reduce()还有什么真正的理由吗？如果您可以通过编写稍微多一点的代码来获得60%的性能提升，为什么还要使用reduce()呢？
编辑:事实上，其他函数方法，如forEach()和map()都表现出类似的性能，比简单的for循环慢至少60%。
这里有一个指向JSPerf测试的链接(使用函数调用)：forloop vs forEach
回答 1
Stack Overflow用户
发布于 2020-09-01 23:24:52
根据数据的大小，这些方法的性能可能会有所不同。速度还受到编译器优化和数据预热的影响。因此，在小型数据上，for of胜出，而在大型reduce上，胜算不大。
您可以通过运行测试来亲自查看：
const LOOP = 3
test(dataGenerator(5))
test(dataGenerator(500))
test(dataGenerator(50000))
test(dataGenerator(500000))
test(dataGenerator(5000000))
function test(dataSet) {
let sum
console.log('Data length:', dataSet.length)
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} reduce`)
sum = dataSet.reduce((s, d) => s += d.data, 0)
console.timeEnd(`${x} reduce`)
}
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} map`)
dataSet.map((i) => sum += i.data)
console.timeEnd(`${x} map`)
}
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} for loop`)
for (let i = 0; i < dataSet.length; i++) {
sum += dataSet[i].data
}
console.timeEnd(`${x} for loop`)
}
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} for reverse`)
for (let i = dataSet.length; i--;) {
sum += dataSet[i].data
}
console.timeEnd(`${x} for reverse`)
}
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} for of`)
for (const item of dataSet) {
sum += item.data
}
console.timeEnd(`${x} for of`)
}
for (let x = 0; x < LOOP; x++) {
sum = 0
console.time(`${x} for each`)
dataSet.forEach(element => {
sum += element.data
})
console.timeEnd(`${x} for each`)
}
console.log()
}
function dataGenerator(rows) {
const dataSet = []
for (let i = 0; i < rows; i++) {
dataSet.push({id: i, data: Math.floor(100 * Math.random())})
}
return dataSet
}这些是在我的笔记本电脑上进行性能测试的结果。与for reverse和for of不同，for loop的工作并不稳定。
➜ node reduce_vs_for.js
Data length: 5
0 reduce: 0.127ms
1 reduce: 0.008ms
2 reduce: 0.006ms
0 map: 0.036ms
1 map: 0.007ms
2 map: 0.018ms
0 for loop: 0.005ms
1 for loop: 0.014ms
2 for loop: 0.004ms
0 for reverse: 0.009ms
1 for reverse: 0.005ms
2 for reverse: 0.004ms
0 for of: 0.008ms
1 for of: 0.004ms
2 for of: 0.004ms
0 for each: 0.046ms
1 for each: 0.003ms
2 for each: 0.003ms
Data length: 500
0 reduce: 0.031ms
1 reduce: 0.027ms
2 reduce: 0.026ms
0 map: 0.039ms
1 map: 0.036ms
2 map: 0.033ms
0 for loop: 0.029ms
1 for loop: 0.028ms
2 for loop: 0.028ms
0 for reverse: 0.027ms
1 for reverse: 0.026ms
2 for reverse: 0.026ms
0 for of: 0.051ms
1 for of: 0.063ms
2 for of: 0.051ms
0 for each: 0.030ms
1 for each: 0.030ms
2 for each: 0.027ms
Data length: 50000
0 reduce: 1.986ms
1 reduce: 1.017ms
2 reduce: 1.017ms
0 map: 2.142ms
1 map: 1.352ms
2 map: 1.310ms
0 for loop: 2.407ms
1 for loop: 12.170ms
2 for loop: 0.246ms
0 for reverse: 0.226ms
1 for reverse: 0.225ms
2 for reverse: 0.223ms
0 for of: 0.217ms
1 for of: 0.213ms
2 for of: 0.215ms
0 for each: 0.391ms
1 for each: 0.409ms
2 for each: 1.020ms
Data length: 500000
0 reduce: 1.920ms
1 reduce: 1.837ms
2 reduce: 1.860ms
0 map: 13.140ms
1 map: 12.762ms
2 map: 14.584ms
0 for loop: 15.325ms
1 for loop: 2.295ms
2 for loop: 2.014ms
0 for reverse: 2.163ms
1 for reverse: 2.138ms
2 for reverse: 2.182ms
0 for of: 1.990ms
1 for of: 2.009ms
2 for of: 2.108ms
0 for each: 2.226ms
1 for each: 2.583ms
2 for each: 2.238ms
Data length: 5000000
0 reduce: 18.763ms
1 reduce: 17.155ms
2 reduce: 26.592ms
0 map: 145.415ms
1 map: 135.946ms
2 map: 144.325ms
0 for loop: 29.273ms
1 for loop: 28.365ms
2 for loop: 21.131ms
0 for reverse: 21.301ms
1 for reverse: 27.779ms
2 for reverse: 29.077ms
0 for of: 19.094ms
1 for of: 19.338ms
2 for of: 26.567ms
0 for each: 22.456ms
1 for each: 26.224ms
2 for each: 20.769ms页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/9629431
复制相关文章
相似问题
腾讯云开发者
