javascript - 从数组创建多维数组

Question

Hello I would like to create in JavaScript multidimensional array like this:

var multiLayer = [
  ["First", "Second", 4],
  [5, 6, 3],
  [3, 2, 1]
];

From simple array like that

var simple = [
  "First",
  "Second",
  4,
  5,
  6,
  3,
  3,
  2,
  1
];

Here is my code yet

var multi = [];
var howMuchBreak = 3;

for (var i = 0; i < simple.length; i++) {
  multi.push(simple[i + howMuchBreak])
}

Variable howMuchBreak defines on which position in the index must be create next nested array.

Answer 1

You can use Array.slice(start, end) and increment the start by the desired sub-array length:

 var simple = [ "First", "Second", 4, 5, 6, 3, 3, 2, 1 ]; var multiLayer = []; // sub array length, in your example 3 var l = 3; for (var i=0; i<simple.length; i += l) { multiLayer.push(simple.slice(i, i+l)); } console.log(multiLayer);

Answer 2

Another solution, using the remainder % operator. The other answer solves the problem in fewer lines (actually, the other answer does it in 18 i do it in 19) but i am adding this just to acquaint you with the % operator, very useful.

Quoting from MDN:

The remainder operator returns the remainder left over when one operand is divided by a second operand.

Ponder the code and try to find out why and how this operator fits your situation :)

 var simple = [ "First", "Second", 4, 5, 6, 3, 3, 2, 1 ]; var multi = []; var sub_array_length = 3; for (var i = 0; i < simple.length; i++) { if(i % sub_array_length === 0) { multi[multi.length] = []; } multi[multi.length - 1].push(simple[i]); } console.log(multi);

Answer 3

or using while...

var arr=[1,2,3,4,5,6,7,8,9,10]
var array = [], chunk = 3;

while (arr.length > 0){ array.push(arr.splice(0, chunk)); }

console.log(array);

Answer 4

I made three variations:

First - Adaptive limiter

What it does is, well, do what you want but adapt if there's space left.

Example:

• Array: [1,2,3,4,5]
• Break by: 2

• Will generate: [ [1,2], [3,4], [5] ]

  var simple = [ "First", "Second", 4, 5, 6, 3, 3, 2, 1 ];

   var multi = []; var howMuchBreak = 2; var i = 0; // start counting simple array elements var x = 0; // start counting limited array elements while (i < simple.length) { var limitedArray = []; x = 0; while (x < howMuchBreak && i < simple.length) { limitedArray.push(simple[i]); x++; i++; } multi.push(limitedArray); }

Second - Non-adaptive limiter

Also does what you want but it doesn't adapt to extra space.

Example:

• Array: [1,2,3,4,5]
• Break by: 2

• Will generate: [ [1,2], [3,4], [5, undefined] ]

  var simple = [ "First", "Second", 4, 5, 6, 3, 3, 2, 1 ];

   var multi = []; var howMuchBreak = 2; var i = 0; // start counting simple array elements var x = 0; // start counting limited array elements while (i < simple.length) { var limitedArray = []; x = 0; while (x < howMuchBreak) { limitedArray.push(simple[i]); x++; i++; } multi.push(limitedArray); }

Third - ES6 API-like

It does the same as the others above but with more elegance. Also, I wanted to introduce you to new features of javascript to improve your code.

That code uses a config JSON with two properties:

• adaptive: <boolean> (defaults to true)
• breakBy: <integer>

Simply pass the simple array first and then the config to the simpleToMulti function:

let multi = simpleToMulti( simpleArray, config );

Example 1:

• Array: [1,2,3,4,5]
• config: { adaptive: true, breakBy: 3 }
• Will generate: [ [1,2,3], [4,5] ]

Example 2:

• Array: [1,2,3,4,5]
• config: { adaptive: false, breakBy: 2 }

• Will generate: [ [1,2], [3,4], [5, undefined] ]

   let simple = ["First", "Second", 4, 5, 6, 3, 3, 2, 1]; let config = { breakBy: 4, adaptive: true }; function simpleToMulti(arr, config) { // normalize config if (config.breakBy === undefined) { console.warn('simpleToMulti: You must inform the breakBy config property'); return; } config.adaptive = config.adaptive === undefined ? true : config.adaptive; // do the magic let limitedArray = []; let multiArray = []; arr.forEach( value => { if (limitedArray.length < config.breakBy) { limitedArray.push(value); } if (limitedArray.length === config.breakBy) { multiArray.push(limitedArray); limitedArray = []; } }); if (limitedArray.length !== 0) { if (config.adaptive) { multiArray.push(limitedArray); } else { while (limitedArray.length < config.breakBy) { limitedArray.push(undefined); } multiArray.push(limitedArray); } } return multiArray; } let multi = simpleToMulti(simple, config); console.log(multi);

Answer 5

I've been spending the last hour trying to find a way to create a multidimensional array from an array of ints. This is what I finally came up with ( reduceRight and times are from the lodash library ).

let dimensions = [1, 2, 3]

_.reduceRight(dimensions, (result, dimension) => {
    return _.times(dimension, () => result)    
}, [])