如何使用JavaScript将长数组拆分为更小的数组
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我有一系列的电子邮件(它可能只是一封电子邮件,或100封电子邮件),我需要发送带有ajax请求的数组(我知道该怎么做),但我只能发送一个包含10个或更少的电子邮件。因此,如果有一个包含20个电子邮件的原始数组,我需要将它们分成2个数组,每个10个。或者如果原始数组中有15个电子邮件,那么1个数组为10,另一个数组为5.我正在使用jQuery,最好的方法是什么?
不要使用jquery ...使用普通的javascript
var a = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
var b = a.splice(0,10);
//a is now [11,12,13,14,15];
//b is now [1,2,3,4,5,6,7,8,9,10];
你可以循环这个来获得你想要的行为。
var a = YOUR_ARRAY;
while(a.length) {
console.log(a.splice(0,10));
}
这将一次给你10个元素...如果你说15个元素,你会得到1-10,你想要的11-15。
你可以看看这段代码。简单有效。
function chunkArrayInGroups(array, unit) {
var results = [],
length = Math.ceil(array.length / unit);
for (var i = 0; i < length; i++) {
results.push(array.slice(i * unit, (i + 1) * unit));
}
return results;
}
chunkArrayInGroups(["a", "b", "c", "d"], 2);
另一个实现,使用Array.reduce(我认为它是唯一缺少的!):
const splitArray = (arr, size) =>
{
if (size === 0) {
return [];
}
return arr.reduce((split, element, index) => {
index % size === 0 ? split.push([element]) : split[Math.floor(index / size)].push(element);
return split;
}, []);
};
正如上面的许多解决方案,这一个是非破坏性的。当大小为0时返回一个空数组只是一个约定。如果省略if
块,则会出现错误,这可能是您想要的。
这是一个简单的一个班轮
var segment = (arr, n) => arr.reduce((r,e,i) => i%n ? (r[r.length-1].push(e), r)
: (r.push([e]), r), []),
arr = Array.from({length: 31}).map((_,i) => i+1);
console.log(segment(arr,7));
对于大型数组,Array.reduce可能效率低下,特别是对于mod运算符。我认为更清洁(也可能更容易阅读)的功能解决方案是这样的:
const chunkArray = (arr, size) =>
arr.length > size
? [arr.slice(0, size), ...chunkArray(arr.slice(size), size)]
: [arr];
如果您想要一个不修改现有数组的方法,请尝试以下方法:
let oldArray = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
let newArray = [];
let size = 3; // Size of chunks you are after
let j = 0; // This helps us keep track of the child arrays
for (var i = 0; i < oldArray.length; i++) {
if (i % size === 0) {
j++
}
if(!newArray[j]) newArray[j] = [];
newArray[j].push(oldArray[i])
}
function chunkArrayInGroups(arr, size) {
var newArr=[];
for (var i=0; arr.length>size; i++){
newArr.push(arr.splice(0,size));
}
newArr.push(arr.slice(0));
return newArr;
}
chunkArrayInGroups([0, 1, 2, 3, 4, 5, 6], 3);
更紧凑:
const chunk = (xs, size) =>
xs.map((_, i) =>
(i % size === 0 ? xs.slice(i, i + size) : null)).filter(Boolean);
// Usage:
const sampleArray = new Array(33).fill(undefined).map((_, i) => i);
console.log(chunk(sampleArray, 5));
var size = 10; var arrayOfArrays = [];
for (var i=0; i<bigarray.length; i+=size) {
arrayOfArrays.push(bigarray.slice(i,i+size));
}
console.log(arrayOfArrays);
与splice()
不同,slice()
对原始阵列没有破坏性。
只需循环遍历数组,拼接它直到全部消耗完为止。
var a = ['a','b','c','d','e','f','g']
, chunk
while (a.length > 0) {
chunk = a.splice(0,3)
console.log(chunk)
}
产量
[ 'a', 'b', 'c' ]
[ 'd', 'e', 'f' ]
[ 'g' ]
你可以使用lodash:https://lodash.com/docs
_.chunk(['a', 'b', 'c', 'd'], 2);
// → [['a', 'b'], ['c', 'd']]
假设您不想销毁原始数组,可以使用这样的代码将长数组拆分为更小的数组,然后可以迭代:
var longArray = []; // assume this has 100 or more email addresses in it
var shortArrays = [], i, len;
for (i = 0, len = longArray.length; i < len; i += 10) {
shortArrays.push(longArray.slice(i, i + 10));
}
// now you can iterate over shortArrays which is an
// array of arrays where each array has 10 or fewer
// of the original email addresses in it
for (i = 0, len = shortArrays.length; i < len; i++) {
// shortArrays[i] is an array of email addresss of 10 or less
}
作为@jyore的answer的补充,如果你仍想保留原始数组:
var originalArray = [1,2,3,4,5,6,7,8];
var splitArray = function (arr, size) {
var arr2 = arr.slice(0),
arrays = [];
while (arr2.length > 0) {
arrays.push(arr2.splice(0, size));
}
return arrays;
}
splitArray(originalArray, 2);
// originalArray is still = [1,2,3,4,5,6,7,8];
另一种方法:
var longArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
var size = 2;
var newArray = new Array(Math.ceil(longArray.length / size)).fill("")
.map(function() { return this.splice(0, size) }, longArray.slice());
// newArray = [[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]];
这不会影响原始数组,因为使用切片制作的副本会传递到map的'this'参数中。
另一个实现:
const arr = ["H", "o", "w", " ", "t", "o", " ", "s", "p", "l", "i", "t", " ", "a", " ", "l", "o", "n", "g", " ", "a", "r", "r", "a", "y", " ", "i", "n", "t", "o", " ", "s", "m", "a", "l", "l", "e", "r", " ", "a", "r", "r", "a", "y", "s", ",", " ", "w", "i", "t", "h", " ", "J", "a", "v", "a", "S", "c", "r", "i", "p", "t"];
const size = 3;
const res = arr.reduce((acc, curr, i) => {
if ( !(i % size) ) { // if index is 0 or can be divided by the `size`...
acc.push(arr.slice(i, i + size)); // ..push a chunk of the original array to the accumulator
}
return acc;
}, []);
// => [["H", "o", "w"], [" ", "t", "o"], [" ", "s", "p"], ["l", "i", "t"], [" ", "a", " "], ["l", "o", "n"], ["g", " ", "a"], ["r", "r", "a"], ["y", " ", "i"], ["n", "t", "o"], [" ", "s", "m"], ["a", "l", "l"], ["e", "r", " "], ["a", "r", "r"], ["a", "y", "s"], [",", " ", "w"], ["i", "t", "h"], [" ", "J", "a"], ["v", "a", "S"], ["c", "r", "i"], ["p", "t"]]
注意 - 这不会修改原始数组。
或者,如果您更喜欢功能性,不可变和自包含的方法:
function splitBy(size, list) {
return list.reduce((acc, curr, i, self) => {
if ( !(i % size) ) {
return [
...acc,
self.slice(i, i + size),
];
}
return acc;
}, []);
}
我也想分享我的解决方案。它有点冗长但也有效。
var data = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15];
var chunksize = 4;
var chunks = [];
data.forEach((item)=>{
if(!chunks.length || chunks[chunks.length-1].length == chunksize)
chunks.push([]);
chunks[chunks.length-1].push(item);
});
console.log(chunks);
输出(格式化):
[ [ 1, 2, 3, 4],
[ 5, 6, 7, 8],
[ 9, 10, 11, 12],
[13, 14, 15 ] ]
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