iterMap

Create an iterator which invokes a function for each iterated value.

Usage

var iterMap = require( '@stdlib/iter/map' );

iterMap( iterator, fcn[, thisArg] )

Returns an iterator which invokes a function for each iterated value.

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

function fcn( v ) {
    return v * 10.0;
}

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

var r = it.next().value;
// returns 10.0

r = it.next().value;
// returns 20.0

r = it.next().value;
// returns 30.0

// ...

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 invoked function is provided two arguments:

  • value: iterated value
  • index: iteration index (zero-based)
var array2iterator = require( '@stdlib/array/to-iterator' );

function fcn( v, i ) {
    return v * (i+1);
}

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

var r = it.next().value;
// returns 1

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

r = it.next().value;
// returns 9

// ...

To set the function execution context, provide a thisArg.

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

function fcn( v ) {
    this.count += 1;
    return v * 10.0;
}

var ctx = {
    'count': 0
};

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

var r = it.next().value;
// returns 10.0

r = it.next().value;
// returns 20.0

r = it.next().value;
// returns 30.0

var count = ctx.count;
// returns 3

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 iterMap = require( '@stdlib/iter/map' );

function scale( v ) {
    return v * 10.0;
}

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

// Create an iterator which scales the generated numbers:
var it = iterMap( rand, scale );

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