test.js

/**
* @license Apache-2.0
*
* Copyright (c) 2018 The Stdlib Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*    http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/

'use strict';

// MODULES //

var tape = require( 'tape' );
var copy = require( '@stdlib/utils/copy' );
var pluck = require( './../lib' );


// TESTS //

tape( 'main export is a function', function test( t ) {
	t.equal( typeof pluck, 'function', 'main export is a function' );
	t.end();
});

tape( 'the function throws an error if not provided an array', function test( t ) {
	var values;
	var i;

	values = [
		'5',
		5,
		NaN,
		true,
		null,
		void 0,
		{},
		function noop() {}
	];

	for ( i = 0; i < values.length; i++ ) {
		t.throws( badValue( values[i] ), TypeError, 'throws an error when provided ' + values[i] );
	}
	t.end();

	function badValue( value ) {
		return function badValue() {
			pluck( value, 'a' );
		};
	}
});

tape( 'the function throws an error if provided an invalid option', function test( t ) {
	t.throws( badOption, TypeError, 'throws an error' );
	t.end();

	function badOption() {
		pluck( [], 'a', {
			'copy': null
		});
	}
});

tape( 'the function returns an empty array if provided an empty array', function test( t ) {
	var out;

	out = pluck( [], 'a' );
	t.deepEqual( out, [], 'returns an empty array' );

	out = pluck( [], 'a', {
		'copy': false
	});
	t.deepEqual( out, [], 'returns an empty array (mutate)' );

	t.end();
});

tape( 'the function plucks a property value from each array element', function test( t ) {
	/* eslint-disable object-curly-newline, object-property-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{ 'a': 1, 'b': 2 },
		{ 'a': 0.5, 'b': 3 }
	];
	expected = [ 1, 0.5 ];

	actual = pluck( arr, 'a' );

	t.deepEqual( actual, expected, 'deep equal' );
	t.end();
});

tape( 'by default, the function returns a new array', function test( t ) {
	/* eslint-disable object-curly-newline, object-property-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{ 'a': 1, 'b': 2 },
		{ 'a': 0.5, 'b': 3 }
	];
	expected = copy( arr );

	actual = pluck( arr, 'a' );

	t.notEqual( actual, arr, 'returns a new array reference' );
	t.deepEqual( arr, expected, 'input array is not mutated' );
	t.end();
});

tape( 'the function supports mutating an input array', function test( t ) {
	/* eslint-disable object-curly-newline, object-property-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{ 'a': 1, 'b': 2 },
		{ 'a': 0.5, 'b': 3 }
	];
	expected = [ 1, 0.5 ];

	actual = pluck( arr, 'a', {
		'copy': false
	});

	t.equal( actual, arr, 'returns same array reference' );
	t.deepEqual( arr, expected, 'input array is mutated' );
	t.end();
});

tape( 'the function skips `undefined` and `null` elements (copy)', function test( t ) {
	/* eslint-disable object-curly-newline, object-property-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{ 'a': 1, 'b': 2 },
		null,
		void 0,
		{ 'a': 0.5, 'b': 3 }
	];

	expected = [ 1, , , 0.5 ]; // eslint-disable-line no-sparse-arrays

	actual = pluck( arr, 'a' );

	t.deepEqual( actual, expected, 'skips undefined and null elements' );
	t.end();
});

tape( 'the function skips `undefined` and `null` elements (mutate)', function test( t ) {
	/* eslint-disable object-curly-newline, object-property-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{ 'a': 1, 'b': 2 },
		null,
		void 0,
		{ 'a': 0.5, 'b': 3 }
	];

	expected = [ 1, null, undefined, 0.5 ];

	actual = pluck( arr, 'a', {
		'copy': false
	});

	t.deepEqual( actual, expected, 'skips undefined and null elements' );
	t.end();
});

tape( 'the function supports non-string property values', function test( t ) {
	var expected;
	var actual;
	var arr;

	arr = [
		[ 0, 1, 2 ],
		[ 3, 4, 5 ]
	];
	expected = [ 1, 4 ];

	actual = pluck( arr, 1 );

	t.deepEqual( actual, expected, 'deep equal' );
	t.end();
});

tape( 'the function does not deep copy plucked values', function test( t ) {
	/* eslint-disable object-curly-newline */
	var expected;
	var actual;
	var arr;

	arr = [
		{
			'a': {
				'b': 2
			}
		},
		{
			'a': {
				'b': 3
			}
		}
	];
	expected = [ { 'b': 2 }, { 'b': 3 } ];

	actual = pluck( arr, 'a' );

	t.deepEqual( actual, expected, 'deep equal' );
	t.equal( actual[0], arr[0].a, 'plucked values are not deep copied' );

	t.end();
});