filter

Return a shallow copy of an array containing only those elements which pass a test implemented by a predicate function.

Usage

var filter = require( '@stdlib/array/base/filter' );

filter( x, predicate[, thisArg] )

Returns a shallow copy of an array containing only those elements which pass a test implemented by a predicate function.

function isPositive( value ) {
    return ( value > 0 );
}

var x = [ 1, -2, -3, 4 ];

var out = filter( x, isPositive );
// returns [ 1, 4 ]

The predicate function is provided three arguments:

value: current array element.
index: current array element index.
arr: input array.

To set the predicate function execution context, provide a thisArg.

function predicate( value ) {
    this.count += 1;
    return ( value > 0 );
}

var x = [ 1, 2, -3, 4 ];

var context = {
    'count': 0
};

var out = filter( x, predicate, context );
// returns [ 1, 2, 4 ]

var cnt = context.count;
// returns 4

Notes

If provided an array-like object having a filter method, the function defers execution to that method and assumes that the method API has the following signature:
```
x.filter( predicate, thisArg )
```
If provided an array-like object without a filter method, the function performs a linear scan and always returns a generic array.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
var naryFunction = require( '@stdlib/utils/nary-function' );
var filter = require( '@stdlib/array/base/filter' );

var x = discreteUniform( 10, -5, 5, {
    'dtype': 'int32'
});
// returns <Int32Array>

var out = filter( x, naryFunction( isPositiveInteger, 1 ) );
// returns <Int32Array>