@stdlib/iter-shift NPM

iterShift

Create an iterator which skips the first value of a provided iterator.

Installation

npm install @stdlib/iter-shift

Usage

var iterShift = require( '@stdlib/iter-shift' );

iterShift( iterator[, clbk[, thisArg]] )

Returns an iterator which skips the first value of a provided iterator.

var array2iterator = require( '@stdlib/array-to-iterator' );

var it = iterShift( array2iterator( [ 1, 2, 3, 4 ] ) );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

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

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.

To invoke a callback upon skipping the first value of a provided iterator, provide a clbk argument.

var array2iterator = require( '@stdlib/array-to-iterator' );

function onShift( v ) {
    console.log( v );
    // => 1
}

var it = iterShift( array2iterator( [ 1, 2, 3, 4 ] ), onShift );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

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

The callback function is provided a single argument:

v: the skipped value

To set the callback execution context, provide a thisArg.

var array2iterator = require( '@stdlib/array-to-iterator' );

function onShift() {
    this.count += 1;
}

var ctx = {
    'count': 0
};

var it = iterShift( array2iterator( [ 1, 2, 3, 4 ] ), onShift, ctx );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 3

v = it.next().value;
// returns 4

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

bool = ( ctx.count === 1 );
// returns true

Notes

If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.

Examples

var randu = require( '@stdlib/random-iter-randu' );
var iterShift = require( '@stdlib/iter-shift' );

// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
    'seed': 1234,
    'iter': 10
});

// Create an iterator which skips the first number:
var it = iterShift( rand );

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

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.