iterShift

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

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 );
}