function sparsearray2iterator( src ) {
	var thisArg;
	var iter;
	var FLG;
	var fcn;
	var get;
	var dt;
	var i;
	if ( !isCollection( src ) ) {
		throw new TypeError( format( 'invalid argument. First argument must be an array-like object. Value: `%s`.', src ) );
	}
	if ( arguments.length > 1 ) {
		fcn = arguments[ 1 ];
		if ( !isFunction( fcn ) ) {
			throw new TypeError( format( 'invalid argument. Second argument must be a function. Value: `%s`.', fcn ) );
		}
		thisArg = arguments[ 2 ];
	}
	i = -1;

	// Create an iterator protocol-compliant object:
	iter = {};
	if ( fcn ) {
		setReadOnly( iter, 'next', next1 );
	} else {
		setReadOnly( iter, 'next', next2 );
	}
	setReadOnly( iter, 'return', end );

	// If an environment supports `Symbol.iterator`, make the iterator iterable:
	if ( iteratorSymbol ) {
		setReadOnly( iter, iteratorSymbol, factory );
	}
	// Resolve an accessor for retrieving array elements (e.g., to accommodate `Complex64Array`, etc):
	dt = dtype( src );
	if ( isAccessorArray( src ) ) {
		get = accessorGetter( dt );
	} else {
		get = getter( dt );
	}
	return iter;

	/**
	* Returns an iterator protocol-compliant object containing the next iterated value.
	*
	* @private
	* @returns {Object} iterator protocol-compliant object
	*/
	function next1() {
		var len;
		if ( FLG ) {
			return {
				'done': true
			};
		}
		len = src.length;
		i += 1;
		while ( i < len && get( src, i ) === void 0 ) {
			i += 1;
		}
		if ( i >= len ) {
			FLG = true;
			return {
				'done': true
			};
		}
		return {
			'value': fcn.call( thisArg, get( src, i ), i, src ),
			'done': false
		};
	}

	/**
	* Returns an iterator protocol-compliant object containing the next iterated value.
	*
	* @private
	* @returns {Object} iterator protocol-compliant object
	*/
	function next2() {
		var len;
		if ( FLG ) {
			return {
				'done': true
			};
		}
		len = src.length;
		i += 1;
		while ( i < len && get( src, i ) === void 0 ) {
			i += 1;
		}
		if ( i >= len ) {
			FLG = true;
			return {
				'done': true
			};
		}
		return {
			'value': get( src, i ),
			'done': false
		};
	}

	/**
	* Finishes an iterator.
	*
	* @private
	* @param {*} [value] - value to return
	* @returns {Object} iterator protocol-compliant object
	*/
	function end( value ) {
		FLG = true;
		if ( arguments.length ) {
			return {
				'value': value,
				'done': true
			};
		}
		return {
			'done': true
		};
	}

	/**
	* Returns a new iterator.
	*
	* @private
	* @returns {Iterator} iterator
	*/
	function factory() {
		if ( fcn ) {
			return sparsearray2iterator( src, fcn, thisArg );
		}
		return sparsearray2iterator( src );
	}
}
Returns an iterator which iterates over each element in a sparse array-like object.

@param {Collection} src - input value
@param {Function} [mapFcn] - function to invoke for each iterated value
@param {*} [thisArg] - execution context
@throws {TypeError} first argument must be an array-like object
@throws {TypeError} second argument must be a function
@returns {Iterator} iterator

@example
var iter = sparsearray2iterator( [ 1, , 3, 4 ] );

var v = iter.next().value;
// returns 1

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

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