比较几种js数组求和的方法

function sumRun(length) {
  // 创建数组
  var array = new Array();
  for (var i = 0; i < length; i++) {
    array.push(i * 2);
  }

  // 1 for循环 
  console.time('for');
  var sum1 = 0;
  for (var i = 0; i < array.length; i++) {
    sum1 += array[i];
  }
  console.timeEnd('for')

  // 2 forEach 
  console.time('forEach');
  var sum2 = 0;
  array.forEach(el => {
    sum2 += el;
  })
  console.timeEnd('forEach')

  // 3 归并方法reduce()和 reduceRight()
  console.time('reduce');
  var sum31 = array.reduce(function (prev, next, index, array) {
    return prev + next;
  })
  console.timeEnd('reduce')

  console.time('reduceRight');
  var sum32 = array.reduceRight(function (last, before, index, array) {
    return last + before;
  })
  console.timeEnd('reduceRight')

  // 4 eval()
  console.time('eval');
  var sum4 = eval(array.join("+"))
  console.timeEnd('eval');

  // 5 map
  console.time('map');
  var sum5 = 0;
  array.map(item => sum5 += item)
  console.timeEnd('map');

  // sum
  var sumArr = [sum1, sum2, [sum31, sum32], sum4, sum5]
  console.log(' ↓ sum1,sum2,[sum31,sum32],sum4,sum5 ↓ ')
  console.log(JSON.stringify(sumArr))
}
sumRun(10000)