Arrays of Data

Arrays of objects are a common data format in JavaScript database connectors and other general data sources.

Numeric datasets commonly use arrays of arrays of numbers.

The "Data Storage" section gives a general overview of common array formats in JavaScript.

The "Functions" section describes the related functions.

Data Storage

Array of Arrays

The spiritual equivalent of the grid in JavaScript is an array of arrays:

Spreadsheet	Array of Arrays
	`[ ["Name", "Index"], ["Bill Clinton", 42], ["GeorgeW Bush", 43], ["Barack Obama", 44], ["Donald Trump", 45], ["Joseph Biden", 46] ]`

Each array within the structure corresponds to one row. Individual data points can be read by indexing by row index and by column index:

var aoa = [
  ["Name", "Index"],
  ["Bill Clinton", 42],
  ["GeorgeW Bush", 43],
  ["Barack Obama", 44],
  ["Donald Trump", 45],
  ["Joseph Biden", 46]
];

var value_at_B4 = aoa[3][1]; // 44
var value_at_A2 = aoa[1][0]; // Bill Clinton

Arrays of Objects

Arrays of objects are commonly used to represent rows from a database:

Spreadsheet	Array of Objects
	`[ { Name: "Bill Clinton", Index: 42 }, { Name: "GeorgeW Bush", Index: 43 }, { Name: "Barack Obama", Index: 44 }, { Name: "Donald Trump", Index: 45 }, { Name: "Joseph Biden", Index: 46 } ]`

Each object within the structure corresponds to one data row. The first row of the spreadsheet is interpreted as the header row.

Functions

The "Input" subsections describe functions that generate SheetJS worksheet objects from arrays of data.

The "Array Output" subsection defines functions that extract data from SheetJS worksheet objects.

Example Sheet

The live examples are based on the following worksheet:

S	h	e	e	t	J	S
1	2			5	6	7
2	3			6	7	8
3	4			7	8	9
4	5	6	7	8	9	0

This table includes duplicate column labels ("e" and "S" appear twice in the first row) and gaps (three data rows have missing fields).

Array of Arrays Input

Create a worksheet from an array of arrays

var ws = XLSX.utils.aoa_to_sheet(aoa, opts);

XLSX.utils.aoa_to_sheet takes an array of arrays of JS values and returns a worksheet resembling the input data. Values are interpreted as follows:

Numbers, Booleans and Strings are stored as the corresponding types.
Date objects are stored as Date cells or date codes (see cellDates option)
Array holes and explicit undefined values are skipped.
null values may be stubbed (see sheetStubs and nullError options)
Cell objects are used as-is.

The function takes an options argument:

Option Name	Default	Description
`dateNF`	FMT 14	Use specified date format in string output
`cellDates`	false	Store dates as type `d` (default is `n`)
`sheetStubs`	false	Create cell objects of type `z` for `null` values
`nullError`	false	If true, emit `#NULL!` error cells for `null` values
`UTC`	false	If true, dates are interpreted using UTC methods **
`dense`	false	Emit dense sheets

UTC option is explained in "Dates"

The following live example reproduces the example worksheet:

Result

Live Editor

function SheetJSExportAOA() {
  /* array of arrays of data */
  var aoa = [
    ["S", "h", "e", "e", "t", "J", "S"],
    [  1,   2,    ,    ,   5,   6,   7],
    [  2,   3,    ,    ,   6,   7,   8],
    [  3,   4,    ,    ,   7,   8,   9],
    [  4,   5,   6,   7,   8,   9,   0]
  ];
  return ( <button onClick={() => {
    /* create worksheet */
    var ws = XLSX.utils.aoa_to_sheet(aoa);
    /* create workbook and export */
    var wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, "Sheet1");
    XLSX.writeFile(wb, "SheetJSExportAOA.xlsx");
  }}>Click to export Array of Arrays</button> );
}

Add data from an array of arrays to an existing worksheet

XLSX.utils.sheet_add_aoa(ws, aoa, opts);

XLSX.utils.sheet_add_aoa takes an array of arrays of JS values and updates an existing worksheet object. It follows the same process as aoa_to_sheet and accepts an options argument:

Option Name	Default	Description
`dateNF`	FMT 14	Use specified date format in string output
`cellDates`	false	Store dates as type `d` (default is `n`)
`sheetStubs`	false	Create cell objects of type `z` for `null` values
`nullError`	false	If true, emit `#NULL!` error cells for `null` values
`origin`		Use specified cell as starting point (see below)
`UTC`	false	If true, dates are interpreted using UTC methods **

UTC option is explained in "Dates"

origin is expected to be one of:

`origin`	Description
(cell object)	Use specified cell (cell object)
(string)	Use specified cell (A1-Style cell)
(number >= 0)	Start from the first column at specified row (0-indexed)
-1	Append to bottom of worksheet starting on first column
(default)	Start from cell `A1`

The example worksheet can be built up in the following order:

Spreadsheet Operations

S	h	e	e	t	J	S
1	2			5	6	7
2	3			6	7	8
3	4			7	8	9
4	5	6	7	8	9	0

aoa_to_sheet([[]]) creates an empty worksheet
sheet_add_aoa writes A1:G1 (red)
sheet_add_aoa writes A2:B4 (blue)
sheet_add_aoa writes E2:G4 (green)
sheet_add_aoa writes A5:G5 (yellow)

/* Start from an empty worksheet */
var ws = XLSX.utils.aoa_to_sheet([[]]);

/* First row */
XLSX.utils.sheet_add_aoa(ws, [ "SheetJS".split("") ], {origin: "A1"});

/* Write data starting at A2 */
XLSX.utils.sheet_add_aoa(ws, [[1,2], [2,3], [3,4]], {origin: "A2"});

/* Write data starting at E2 */
XLSX.utils.sheet_add_aoa(ws, [[5,6,7], [6,7,8], [7,8,9]], {origin:{r:1, c:4}});

/* Append row */
XLSX.utils.sheet_add_aoa(ws, [[4,5,6,7,8,9,0]], {origin: -1});

Result

Live Editor

function SheetJSAddAOA() { return ( <button onClick={() => {
  /* Start from an empty worksheet */
  var ws = XLSX.utils.aoa_to_sheet([[]]);

  /* First row */
  XLSX.utils.sheet_add_aoa(ws, [ "SheetJS".split("") ], {origin: "A1"});

  /* Write data starting at A2 */
  XLSX.utils.sheet_add_aoa(ws, [[1,2], [2,3], [3,4]], {origin: "A2"});

  /* Write data starting at E2 */
  XLSX.utils.sheet_add_aoa(ws, [[5,6,7], [6,7,8], [7,8,9]], {origin:{r:1, c:4}});

  /* Append row */
  XLSX.utils.sheet_add_aoa(ws, [[4,5,6,7,8,9,0]], {origin: -1});

  /* create workbook and export */
  var wb = XLSX.utils.book_new();
  XLSX.utils.book_append_sheet(wb, ws, "Sheet1");
  XLSX.writeFile(wb, "SheetJSAddAOA.xlsx");
}}>Click to export Array of Arrays</button> ); }

Array of Objects Input

Create a worksheet from an array of objects

var ws = XLSX.utils.json_to_sheet(aoo, opts);

XLSX.utils.json_to_sheet takes an array of objects and returns a worksheet with automatically-generated "headers" based on the keys of the objects. The default column order is determined by the first appearance of the field using Object.keys. The function accepts an options argument:

Option Name	Default	Description
`header`		Use specified field order (default `Object.keys`) **
`dateNF`	FMT 14	Use specified date format in string output
`cellDates`	false	Store dates as type `d` (default is `n`)
`skipHeader`	false	If true, do not include header row in output
`nullError`	false	If true, emit `#NULL!` error cells for `null` values
`UTC`	false	If true, dates are interpreted using UTC methods **
`dense`	false	Emit dense sheets

UTC option is explained in "Dates"

All fields from each row will be written! header hints at a particular order but is not exclusive. To remove fields from the export, filter the data source.

Some data sources have special options to filter properties. For example, MongoDB will add the _id field when finding data from a collection:

const aoo_with_id = await coll.find({}).toArray();
const ws = XLSX.utils.json_to_sheet(aoo_with_id); // includes _id column

This can be filtered out through the projection property:

const aoo = await coll.find({}, {projection:{_id:0}}).toArray(); // no _id !
const ws = XLSX.utils.json_to_sheet(aoo);

If a data source does not provide a filter option, it can be filtered manually:

const aoo = data.map(obj => Object.fromEntries(Object.entries(obj).filter(r => headers.indexOf(r[0]) > -1)));

If header is an array, missing keys will be added in order of first use.
Cell types are deduced from the type of each value. For example, a Date object will generate a Date cell, while a string will generate a Text cell.
Null values will be skipped by default. If nullError is true, an error cell corresponding to #NULL! will be written to the worksheet.

Result

Live Editor

function SheetJSExportAOO() {
  /* array of arrays of data */
  var aoo = [
    { Name: "Bill Clinton", Index: 42 },
    { Name: "GeorgeW Bush", Index: 43 },
    { Name: "Barack Obama", Index: 44 },
    { Name: "Donald Trump", Index: 45 },
    { Name: "Joseph Biden", Index: 46 }
  ];
  return ( <button onClick={() => {
    /* create worksheet */
    var ws = XLSX.utils.json_to_sheet(aoo);
    /* create workbook and export */
    var wb = XLSX.utils.book_new();
    XLSX.utils.book_append_sheet(wb, ws, "Sheet1");
    XLSX.writeFile(wb, "SheetJSExportAOO.xlsx");
  }}>Click to export Array of Objects</button> );
}

The example sheet cannot be reproduced using plain objects since JS object keys must be unique.

Typically the original data source will have different column names. After writing with json_to_sheet, the aoa_to_sheet method can rewrite the headers:

/* original array of objects */
var data = [
  { S:1, h:2,             t:5, J:6, S_1:7 },
  { S:2, h:3,             t:6, J:7, S_1:8 },
  { S:3, h:4,             t:7, J:8, S_1:9 },
  { S:4, h:5, e:6, e_1:7, t:8, J:9, S_1:0 },
];

/* column order for the generated worksheet */
//                 |  A  | B  | C |  D   |  E |  F |  G    |
var data_headers = [ "S", "h", "e", "e_1", "t", "J", "S_1" ];

/* new headers for the first row of the worksheet */
//                 |  A  | B  | C |  D   |  E |  F |  G    |
var new_headers  = [ "S", "h", "e", "e",   "t", "J", "S"   ];

/* write data with using data headers */
var ws = XLSX.utils.json_to_sheet(data, { header: data_headers });

/* replace first row */
XLSX.utils.sheet_add_aoa(worksheet, [new_headers], { origin: "A1" });

Add data from an array of objects to an existing worksheet

XLSX.utils.sheet_add_json(ws, aoo, opts);

XLSX.utils.sheet_add_json takes an array of objects and updates an existing worksheet object. It follows the same process as json_to_sheet and accepts an options argument:

Option Name	Default	Description
`header`		Use specified column order (default `Object.keys`)
`dateNF`	FMT 14	Use specified date format in string output
`cellDates`	false	Store dates as type `d` (default is `n`)
`skipHeader`	false	If true, do not include header row in output
`nullError`	false	If true, emit `#NULL!` error cells for `null` values
`origin`		Use specified cell as starting point (see below)
`UTC`	false	If true, dates are interpreted using UTC methods **

UTC option is explained in "Dates"

origin is expected to be one of:

`origin`	Description
(cell object)	Use specified cell (cell object)
(string)	Use specified cell (A1-Style cell)
(number >= 0)	Start from the first column at specified row (0-indexed)
-1	Append to bottom of worksheet starting on first column
(default)	Start from cell `A1`

This example worksheet can be built up in the order A1:G1, A2:B4, E2:G4, A5:G5:

/* Start from an empty worksheet */
var ws = XLSX.utils.aoa_to_sheet([[]]);

/* Header order */
var header = ["A", "B", "C", "D", "E", "F", "G"];

/* First row */
XLSX.utils.sheet_add_json(ws, [
  { A: "S", B: "h", C: "e", D: "e", E: "t", F: "J", G: "S" }
], {header: header, skipHeader: true});

/* Write data starting at A2 */
XLSX.utils.sheet_add_json(ws, [
  { A: 1, B: 2 }, { A: 2, B: 3 }, { A: 3, B: 4 }
], {header: header, skipHeader: true, origin: "A2"});

/* Write data starting at E2 */
XLSX.utils.sheet_add_json(ws, [
  { A: 5, B: 6, C: 7 }, { A: 6, B: 7, C: 8 }, { A: 7, B: 8, C: 9 }
], {header: ["A", "B", "C"], skipHeader: true, origin: { r: 1, c: 4 }});

/* Append row */
XLSX.utils.sheet_add_json(ws, [
  { A: 4, B: 5, C: 6, D: 7, E: 8, F: 9, G: 0 }
], {header: header, skipHeader: true, origin: -1});

If the header option is an array, sheet_add_json and sheet_to_json will append missing elements.

This design enables consistent header order across calls:

Result

Live Editor

function SheetJSHeaderOrder() {
  /* Use shared header */
  const header = [];
  const ws1 = XLSX.utils.json_to_sheet([ {C: 2, D: 3}, ], {header});
  XLSX.utils.sheet_add_json(ws1, [ {D: 1, C: 4}, ], {header, origin: -1, skipHeader: true});

  /* only use header in first call */
  const ws2 = XLSX.utils.json_to_sheet([ {C: 2, D: 3}, ], {header:[]});
  XLSX.utils.sheet_add_json(ws2, [ {D: 1, C: 4}, ], {origin: -1, skipHeader: true});

  return (<pre>
    <b>Objects</b>
    {"\n[\n  { C: 2, D: 3 },\n  { D: 1, C: 4 } // different key order\n]\n"}<br/>
    <b>Worksheet when same `header` array is passed to `sheet_add_json`</b>
    <div dangerouslySetInnerHTML={{__html:XLSX.utils.sheet_to_html(ws1)}}/>
    <i>New contents of `header`</i><br/>
    {JSON.stringify(header)}<br/>
    <br/>
    <b>Worksheet when no `header` property is passed to `sheet_add_json`</b>
    <div dangerouslySetInnerHTML={{__html:XLSX.utils.sheet_to_html(ws2)}}/>
  </pre>)
}

Array Output

JavaScript
TypeScript

var arr = XLSX.utils.sheet_to_json(ws, opts);

var aoa = XLSX.utils.sheet_to_json(ws, {header: 1, ...other_opts});

TypeScript types are purely informational. They are not included at run time and do not influence the behavior of the sheet_to_json function.

sheet_to_json does not perform field validation!

The main type signature treats each row as any:

const data: any[] = XLSX.utils.sheet_to_json(ws, opts);

The any[][] overload is designed for use with header: 1 (array of arrays):

const aoa: any[][] = XLSX.utils.sheet_to_json(ws, { header: 1, ...other_opts });

An interface can be passed as a generic parameter. sheet_to_json will still return an array of plain objects (the types do not affect runtime behavior):

interface President {
  Name: string;
  Index: number;
}

const data: President[] = XLSX.utils.sheet_to_json<President>(ws);

XLSX.utils.sheet_to_json generates an array of JS objects. The function takes an options argument:

Option Name	Default	Description
`raw`	`true`	Use raw values (true) or formatted strings (false)
`range`	**	Override Range (see table below)
`header`		Control output format (see table below)
`dateNF`	FMT 14	Use specified date format in string output
`defval`		Use specified value in place of null or undefined
`blankrows`	**	Include blank lines in the output **
`skipHidden`	false	Do not generate objects for hidden rows/columns
`UTC`	false	If true, dates will be correct in UTC **

raw only affects cells which have a format code (.z) field or a formatted text (.w) field.
If header is specified, the first row is considered a data row; if header is not specified, the first row is the header row and not considered data.
When header is not specified, the conversion will automatically disambiguate header entries by affixing _ and a count starting at 1. For example, if three columns have header foo the output fields are foo, foo_1, foo_2
null values are returned when raw is true but are skipped when false.
If defval is not specified, null and undefined values are skipped normally. If specified, all null and undefined points will be filled with defval
When header is 1, the default is to generate blank rows. blankrows must be set to false to skip blank rows.
When header is not 1, the default is to skip blank rows. blankrows must be true to generate blank rows
UTC option is explained in "Dates"

range is expected to be one of:

`range`	Description
(number)	Use worksheet range but set starting row to the value
(string)	Use specified range (A1-Style bounded range string)
(default)	Use worksheet range (`ws['!ref']`)

header is expected to be one of:

`header`	Description
`1`	Generate an array of arrays
`"A"`	Row object keys are literal column labels
array of strings	Use specified strings as keys in row objects
(default)	Read and disambiguate first row as keys

If header is not 1, the row object will contain the non-enumerable property __rowNum__ that represents the row of the sheet corresponding to the entry.
If header is an array, the keys will not be disambiguated. This can lead to unexpected results if the array values are not unique!

For the example worksheet:

Result

Live Editor

function SheetJSToJSON() {
  /* original data */
  var ws = XLSX.utils.aoa_to_sheet([
    ["S", "h", "e", "e", "t", "J", "S"],
    [  1,   2,    ,    ,   5,   6,   7],
    [  2,   3,    ,    ,   6,   7,   8],
    [  3,   4,    ,    ,   7,   8,   9],
    [  4,   5,   6,   7,   8,   9,   0]
  ]);

  /* display JS objects with some whitespace */
  const aoo = o => o.map(r => "  " + JSON.stringify(r).replace(/,"/g, ', "').replace(/:/g, ": ").replace(/"([A-Za-z_]\w*)":/g, '$1:')).join("\n");
  const aoa = o => o.map(r => "  " + JSON.stringify(r).replace(/,/g, ', ').replace(/null/g, "")).join("\n");

  return ( <pre>
    <b>Worksheet (as HTML)</b>
    <div dangerouslySetInnerHTML={{__html: XLSX.utils.sheet_to_html(ws)}}/>
    <b>XLSX.utils.sheet_to_json(ws, {'{'} header: 1 {'}'}) [array of arrays]</b><br/>
    [<br/>{aoa(XLSX.utils.sheet_to_json(ws, { header: 1 }))}<br/>]<br/><br/>
    <b>XLSX.utils.sheet_to_json(ws) [objects with header disambiguation]</b><br/>
    [<br/>{aoo(XLSX.utils.sheet_to_json(ws))}<br/>]<br/><br/>
    <b>XLSX.utils.sheet_to_json(ws, {'{'} header: "A" {'}'}) [column names as keys]</b><br/>
    [<br/>{aoo(XLSX.utils.sheet_to_json(ws, { header: "A" }))}<br/>]<br/><br/>
    <b>XLSX.utils.sheet_to_json(ws, {'{'} header: ["A","E","I","O","U","6","9"] {'}'})</b><br/>
    [<br/>{aoo(XLSX.utils.sheet_to_json(ws, { header: ["A","E","I","O","U","6","9"] }))}<br/>]<br/>
  </pre> );
}

Data Storage​

Array of Arrays​

Arrays of Objects​

Functions​

Example Sheet​

Array of Arrays Input​

Array of Objects Input​

Array Output​

Data Storage

Array of Arrays

Arrays of Objects

Functions

Example Sheet

Array of Arrays Input

Array of Objects Input

Array Output