JavaScript 中的分区

Partitioning in JavaScript

提问by 500

Please consider an array such as :

请考虑一个数组，例如：

arrayAll = [1,2,3,4,5,6,7,8,9]

Is there a package that enable to do partitioning to obtain :

是否有一个包可以进行分区以获得：

arrayALLPartionned = [[1,2,3],[4,5,6],[7,8,9]]

I can see how to do this with a for loop but would appreciate a "pre-made" function if existing.

我可以看到如何使用 for 循环执行此操作，但如果存在“预制”函数，我将不胜感激。

采纳答案by millimoose

If using Underscore.js, you can implement this with groupBy()and values()

如果使用Underscore.js，您可以使用groupBy()和values()

function partition(items, size) {
    var result = _.groupBy(items, function(item, i) {
        return Math.floor(i/size);
    });
    return _.values(result);
}

(This is less ugly in CoffeeScript.)

（这在 CoffeeScript 中不那么难看。）

jsFiddle: http://jsfiddle.net/MW3BS/

jsFiddle：http: //jsfiddle.net/MW3BS/

回答by starbeamrainbowlabs

I think you will have to use a for loop, don't know of any inbuilt functions...

我认为你将不得不使用 for 循环，不知道任何内置函数......

Try this function:

试试这个功能：

function splitarray(input, spacing)
{
    var output = [];

    for (var i = 0; i < input.length; i += spacing)
    {
        output[output.length] = input.slice(i, i + spacing);
    }

    return output;
}

回答by millimoose

Here's a recursive solution:

这是一个递归解决方案：

function partition(array, n) {
  return array.length ? [array.splice(0, n)].concat(partition(array, n)) : [];
}    

This takes advantage of the fact that Array#splicedestructively remove the specified items, and returns them as the function value. Note that this will destroy the input array, leaving it empty.

这利用了Array#splice破坏性删除指定项目的事实，并将它们作为函数值返回。请注意，这将破坏输入数组，使其为空。

回答by Ross

I've added this solution to @dystroy's jspref hereand it appearsto run twice as fast as the other solutions. Edit: in Safari & Chrome but not Firefox

我已将此解决方案添加到@dystroy 的 jspref 中，它的运行速度似乎是其他解决方案的两倍。编辑：在 Safari 和 Chrome 但不是 Firefox

Here is functional style solution to add to the mix of answers here.

这是功能样式解决方案，可添加到此处的答案组合中。

It is a higher order function called toPartitionswhich returns a callback for underscore's reduce method or the native array reduce method.

它是一个被调用的高阶函数toPartitions，它返回下划线的 reduce 方法或本机数组 reduce 方法的回调。

Example usage:

用法示例：

[1,2,3,4,5,6,7,8,9].reduce( toPartitions( 3 ), [] );

The function:

功能：

function toPartitions ( size ) {
    var partition = [];
    return function ( acc, v ) {
        partition.push( v );
        if ( partition.length === size ) {
            acc.push( partition );
            partition = [];
        }
        return acc;
    };
}

Like Clojure's partitionit will not include a tail partition when there are not enough elements.

与 Clojure 的分区一样，当元素不足时，它不会包含尾分区。

In your example you could do:

在您的示例中，您可以执行以下操作：

arrayALLPartionned = arrayAll.reduce( toPartitions( 3 ), [] ) );

If you don't want to use this with reduce, but just have a function which takes an array and partition size you could do:

如果您不想将其与 一起使用reduce，而只想使用一个接受数组和分区大小的函数，您可以执行以下操作：

function partition ( arr, size ) {
    return arr.reduce( toPartitions( size ), [] );
}

Therefore the solution would just be:

因此，解决方案将是：

arrayALLPartionned = partition( arrayAll, 3 );

回答by Denys Séguret

One more solution, with no external library :

另一种解决方案，没有外部库：

function partition(items, size) {
    var p = [];
    for (var i=Math.floor(items.length/size); i-->0; ) {
        p[i]=items.slice(i*size, (i+1)*size);
    }
    return p;
}

Demonstration : http://jsfiddle.net/dystroy/xtHXZ/

演示：http: //jsfiddle.net/dystroy/xtHXZ/

回答by Andy

Prototype has an array.partition function as well as an eachSlice() function. Sounds like eachSlice() is what you're looking for. If you're using jquery, there's a plug in to be able to use prototype functions. Here's a link to it... http://www.learningjquery.com/2009/02/implementing-prototypes-array-methods-in-jquery

Prototype 有一个 array.partition 函数以及一个 eachSlice() 函数。听起来 eachSlice() 就是你要找的。如果您使用 jquery，有一个插件可以使用原型函数。这是它的链接... http://www.learningjquery.com/2009/02/implementing-prototypes-array-methods-in-jquery

回答by Peter Olson

You can write your own prototype method to do this

您可以编写自己的原型方法来执行此操作

Array.prototype.partition = function(length) {
  var result = [];
  for(var i = 0; i < this.length; i++) {
    if(i % length === 0) result.push([]);
    result[result.length - 1].push(this[i]);
  }
  return result;
};

If you prefer not to add to the native prototype, you can write a simple function:

如果你不想添加到原生原型，你可以写一个简单的函数：

var partition = function(arr, length) {
  var result = [];
  for(var i = 0; i < arr.length; i++) {
    if(i % length === 0) result.push([]);
    result[result.length - 1].push(arr[i]);
  }
  return result;
};

You can see it in action on this jsFiddle demo.

你可以在这个 jsFiddle demo 上看到它的实际效果。