bifurcateIndicesBy

Split element indices into two groups according to a predicate function.

Usage

var bifurcateIndicesBy = require( '@stdlib/array/base/bifurcate-indices-by' );

bifurcateIndicesBy( x, predicate[, thisArg] )

Splits element indices into two groups according to a predicate function.

function predicate( v ) {
    return v[ 0 ] === 'b';
}

var x = [ 'beep', 'boop', 'foo', 'bar' ];

var out = bifurcateIndicesBy( x, predicate );
// returns [ [ 0, 1, 3 ], [ 2 ] ]

A predicate function is provided the following 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( v ) {
    this.count += 1;
    return v[ 0 ] === 'b';
}

var x = [ 'beep', 'boop', 'foo', 'bar' ];

var context = {
    'count': 0
};
var out = bifurcateIndicesBy( x, predicate, context );
// returns [ [ 0, 1, 3 ], [ 2 ] ]

var cnt = context.count;
// returns 4

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var take = require( '@stdlib/array/base/take-indexed' );
var bifurcateIndicesBy = require( '@stdlib/array/base/bifurcate-indices-by' );

function predicate( v ) {
    // Use the first letter of each element to define groups:
    return v[ 0 ] === 'b';
}

// Define an initial array of values:
var values = [ 'beep', 'boop', 'foo', 'bar', 'woot', 'woot' ];

// Sample from the initial array to generate a random collection:
var indices = discreteUniform( 100, 0, values.length-1, {
    'dtype': 'generic'
});
var x = take( values, indices );
// returns [...]

// Split the values:
var out = bifurcateIndicesBy( x, predicate );
// returns [...]

console.log( out );