iterForEach
Create an iterator which invokes a function for each iterated value before returning the iterated value.
Usage
var iterForEach = require( '@stdlib/iter/for-each' );
iterForEach( iterator, fcn[, thisArg] )
Returns an iterator which invokes a function for each iterated value before returning the iterated value.
var array2iterator = require( '@stdlib/array/to-iterator' );
function assert( v ) {
if ( v !== v ) {
throw new Error( 'should not be NaN' );
}
}
var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert );
// returns <Object>
var r = it.next().value;
// returns 1
r = it.next().value;
// returns 2
r = it.next().value;
// returns 3
// ...
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
valueproperty and adoneproperty having abooleanvalue 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 assert( v, i ) {
if ( i < 0 ) {
throw new Error( 'unexpected Error' );
}
}
var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert );
// returns <Object>
var r = it.next().value;
// returns 1
r = it.next().value;
// returns 2
r = it.next().value;
// returns 3
// ...
To set the execution context for fcn, provide a thisArg.
var array2iterator = require( '@stdlib/array/to-iterator' );
function assert( v ) {
this.count += 1;
if ( v !== v ) {
throw new Error( 'should not be NaN' );
}
}
var ctx = {
'count': 0
};
var it = iterForEach( array2iterator( [ 1, 2, 3, 4 ] ), assert, ctx );
// returns <Object>
var r = it.next().value;
// returns 1
r = it.next().value;
// returns 2
r = it.next().value;
// returns 3
var count = ctx.count;
// returns 3
Notes
- If an environment supports
Symbol.iteratorand a provided iterator is iterable, the returned iterator is iterable.
Examples
var randu = require( '@stdlib/random/iter/randu' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var iterForEach = require( '@stdlib/iter/for-each' );
function assert( v ) {
if ( isnan( v ) ) {
throw new Error( 'should not be NaN' );
}
}
// Create a seeded iterator for generating pseudorandom numbers:
var rand = randu({
'seed': 1234,
'iter': 10
});
// Create an iterator which validates generated numbers:
var it = iterForEach( rand, assert );
// Perform manual iteration...
var r;
while ( true ) {
r = it.next();
if ( r.done ) {
break;
}
console.log( r.value );
}