Flatten an array.
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> Flatten an array.
``bash`
npm install @stdlib/utils-flatten-array
`javascript`
var flattenArray = require( '@stdlib/utils-flatten-array' );
#### flattenArray( arr\[, options] )
Flattens an array.
`javascript
var arr = [ 1, [2, [3, [4, [ 5 ], 6], 7], 8], 9 ];
var out = flattenArray( arr );
// returns [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
`
The function accepts the following options:
- depth: maximum depth to flatten.
- copy: boolean indicating whether to deep [copy][@stdlib/utils/copy] array elements. Default: false.
To flatten to a specified depth, set the depth option.
`javascript
var arr = [ 1, [2, [3, [4, [ 5 ], 6], 7], 8], 9 ];
var out = flattenArray( arr, {
'depth': 2
});
// returns [ 1, 2, 3, [4, [5], 6], 7, 8, 9 ]
var bool = ( arr[1][1][1] === out[3] );
// returns true
`
To deep [copy][@stdlib/utils/copy] array elements, set the copy option to true.
`javascript
var arr = [ 1, [2, [3, [4, [ 5 ], 6], 7], 8], 9 ];
var out = flattenArray( arr, {
'depth': 2,
'copy': true
});
// returns [ 1, 2, 3, [4, [5], 6], 7, 8, 9 ]
var bool = ( arr[1][1][1] === out[3] );
// returns false
`
#### flattenArray.factory( dims\[, options] )
Returns a function optimized for flattening arrays having specified dimensions.
`javascript
var flatten = flattenArray.factory( [ 3, 3 ] );
var arr = [
[ 1, 2, 3 ],
[ 4, 5, 6 ],
[ 7, 8, 9 ]
];
var out = flatten( arr );
// returns [ 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
arr = [
[ 11, 12, 13 ],
[ 14, 15, 16 ],
[ 17, 18, 19 ]
];
out = flatten( arr );
// returns [ 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
`
The function accepts the following options:
- copy: boolean indicating whether to deep [copy][@stdlib/utils/copy] array elements. Default: false.
To deep [copy][@stdlib/utils/copy] array elements, set the copy option to true.
`javascript
var flatten = flattenArray.factory( [ 3, 3 ], {
'copy': true
});
var arr = [
[ 1, 2, 3 ],
[ 4, { 'x': 5 }, 6 ],
[ 7, 8, 9 ]
];
var out = flatten( arr );
// returns [ 1, 2, 3, 4, {'x':5}, 6, 7, 8, 9 ]
var bool = ( arr[1][1] === out[4] );
// returns false
`
- A flatten function returned by the factory method does not validate that input arrays actually have the specified dimensions.factory
- The method uses code evaluation, which may be problematic in browser contexts enforcing a strict [content security policy][mdn-csp] (CSP).
`javascript
var flattenArray = require( '@stdlib/utils-flatten-array' );
function tensor( N, M, L ) {
var tmp1;
var tmp2;
var out;
var i;
var j;
var k;
out = [];
for ( i = 0; i < N; i++ ) {
tmp1 = [];
for ( j = 0; j < M; j++ ) {
tmp2 = [];
for ( k = 0; k < L; k++ ) {
tmp2.push( (MLi) + (j*L) + k + 1 );
}
tmp1.push( tmp2 );
}
out.push( tmp1 );
}
return out;
}
// Define array dimensions:
var N = 1000;
var M = 100;
var L = 10;
// Create a 3-dimensional nested array:
var data = tensor( N, M, L );
// Create a flattened (strided) array from a 3-dimensional nested array:
var arr = flattenArray( data );
// To access the data[4][20][2] element...
var xStride = M * L;
var yStride = L;
var zStride = 1;
var v = arr[ (4xStride) + (20yStride) + (2*zStride) ];
// returns 4203
var bool = ( data[4][20][2] === v );
// returns true
`
*
- [@stdlib/utils-flatten-object][@stdlib/utils/flatten-object]: flatten an object.
*
This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].
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---
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