vararray = [1,2,3,4,5]
varsum =0
1.for循环
for(leti =0i <array.lengthi++) {
sum += array[i]
}
2.forEach
array.forEach(ele=>{
sum += ele
})
3.归并方法reduce()和 reduceRight()
//这两个方法都会迭代数组的所有项,然后构建一个最终返回的值。其中, reduce()方法从数组的第一项开始,逐个遍历到最后。
//而 reduceRight()则从数组的最后一项开始,向前遍历到第一项
varsum1 = array.reduce(function(prev, next, index, array){
returnprev + next
})
varsum2 = array.reduceRight(function(last, before, index, array){
returnlast + before
})
4.eval()
eval(array.join("+"))
var trans = function (arr, index, value) {var length = arr.length
if (index > length)
return arr
arr = arr.slice(0, index)
while (arr.length < length) {
arr.push(value++)
}
return arr
}
var arr = [0, 1, 2, 3, 4, 5, 6, 7, 8]
console.log(trans(arr, 2, 4))