@stdlib/iter-datespace

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iterDatespace

Create an iterator which returns evenly spaced dates over a specified interval.

Installation

npm install @stdlib/iter-datespace

Usage

var iterDatespace = require( '@stdlib/iter-datespace' );

iterDatespace( start, stop[, N][, options] )

Returns an iterator which returns evenly spaced Date objects over a specified interval.

var MILLISECONDS_IN_DAY = require( '@stdlib/constants-time-milliseconds-in-day' );

var start = ( new Date() ).getTime();
var it = iterDatespace( start, start+MILLISECONDS_IN_DAY );
// returns <Object>

var v = it.next().value;
// returns <Date>

v = it.next().value;
// returns <Date>

v = it.next().value;
// returns <Date>

// ...

The returned iterator protocol-compliant object has the following properties:

• next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
• return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.

The function accepts the following options:

• round: specifies how sub-millisecond times should be rounded: 'floor', 'ceil', or 'round'. Default: 'floor'.

By default, the iterator returns 100 values. To return an alternative number of values over the specified interval, provide an N argument.

var MILLISECONDS_IN_DAY = require( '@stdlib/constants-time-milliseconds-in-day' );

var start = ( new Date() ).getTime();
var it = iterDatespace( start, start+MILLISECONDS_IN_DAY, 3 );
// returns <Object>

var v = it.next().value;
// returns <Date>

v = it.next().value;
// returns <Date>

v = it.next().value;
// returns <Date>

var bool = it.next().done;
// returns true

The returned iterator is guaranteed to return the start and stop values. Beware, however, that values between start and stop are subject to rounding errors. For example,

var it = iterDatespace( 1417503655000, 1417503655001, 3 );
// returns <Object>

var v = it.next().value.getTime();
// returns 1417503655000

v = it.next().value.getTime();
// returns 1417503655000

v = it.next().value.getTime();
// returns 1417503655001

where sub-millisecond values are truncated by the Date constructor. Duplicate values should only be a problem when the interval separating consecutive times is less than a millisecond. As the interval separating consecutive dates goes to infinity, the quantization noise introduced by millisecond resolution is negligible.

By default, fractional timestamps are floored. To specify that timestamps always be rounded up or to the nearest millisecond when converted to Date objects, set the round option.

var opts = {
    'round': 'ceil'
};
var it = iterDatespace( 1417503655000, 1417503655001, 3, opts );
// returns <Object>

var v = it.next().value.getTime();
// returns 1417503655000

v = it.next().value.getTime();
// returns 1417503655001

v = it.next().value.getTime();
// returns 1417503655001

opts = {
    'round': 'round'
};
it = iterDatespace( 1417503655000, 1417503655001, 3, opts );
// returns <Object>

v = it.next().value.getTime();
// returns 1417503655000

v = it.next().value.getTime();
// returns 1417503655001

v = it.next().value.getTime();
// returns 1417503655001

Notes

• The start and stop arguments may be either Date objects, JavaScript timestamps (i.e., millisecond timestamps), or a valid date string.
• If an environment supports Symbol.iterator, the returned iterator is iterable.

Examples

var MILLISECONDS_IN_DAY = require( '@stdlib/constants-time-milliseconds-in-day' );
var HOURS_IN_DAY = require( '@stdlib/constants-time-hours-in-day' );
var iterDatespace = require( '@stdlib/iter-datespace' );

// Create an iterator which returns a Date object for each hour in the next 24 hours:
var start = new Date();
var end = new Date( start.getTime()+MILLISECONDS_IN_DAY );
var it = iterDatespace( start, end, HOURS_IN_DAY+1 );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
        break;
    }
    console.log( v.value );
}

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See Also

• @stdlib/array-from-iterator: create (or fill) an array from an iterator.
• @stdlib/iter-incrspace: create an iterator which returns evenly spaced numbers according to a specified increment.
• @stdlib/iter-linspace: create an iterator which returns evenly spaced numbers over a specified interval.
• @stdlib/iter-logspace: create an iterator which returns evenly spaced numbers on a log scale.
• @stdlib/iter-step: create an iterator which returns a sequence of numbers according to a specified increment.

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Notice

This package is part of 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, see the main project repository.

Community

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License

See LICENSE.

Copyright

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