@stdlib/iter/cunone-by/README.md

Standard iterator utilities.

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# iterCuNoneBy

> Create an iterator which cumulatively tests whether every iterated value fails a test implemented by a predicate function.

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## Usage

```javascript
var iterCuNoneBy = require( '@stdlib/iter/cunone-by' );
```

#### iterCuNoneBy( iterator, predicate\[, thisArg] )

Returns an [iterator][mdn-iterator-protocol] which cumulatively tests whether every iterated value fails a test implemented by a `predicate` function.

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

function predicate( v ) {
    return ( v > 0 );
}

var arr = array2iterator( [ 0, 0, 0, 1, 0 ] );

var it = iterCuNoneBy( arr, predicate );

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

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

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

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

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

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

The returned [iterator][mdn-iterator-protocol] protocol-compliant object has the following properties:

-   **next**: function which returns an [iterator][mdn-iterator-protocol] 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][mdn-iterator-protocol] is finished.
-   **return**: function which closes an [iterator][mdn-iterator-protocol] and returns a single (optional) argument in an [iterator][mdn-iterator-protocol] protocol-compliant object.

A `predicate` function is provided two arguments:

-   **value**: iterated value
-   **index**: iteration index (zero-based)

To set the `predicate` function execution context, provide a `thisArg`.

<!-- eslint-disable no-invalid-this -->

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

function predicate( v ) {
    this.count += 1;
    return ( v < 0 );
}

var ctx = {
    'count': 0
};

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

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

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

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

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

var count = ctx.count;
// returns 4
```

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<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->

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## Notes

-   A `predicate` function is invoked for each iterated value until the first truthy `predicate` function return value. Upon encountering the first truthy return value, the returned iterator ceases to invoke the `predicate` function and returns `false` for each subsequent iterated value of the provided input `iterator`.

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## Examples

<!-- eslint no-undef: "error" -->

```javascript
var randu = require( '@stdlib/random/iter/randu' );
var iterCuNoneBy = require( '@stdlib/iter/cunone-by' );

function threshold( r ) {
    return ( r > 0.95 );
}

// Create an iterator which generates uniformly distributed pseudorandom numbers:
var opts = {
    'iter': 100
};
var riter = randu( opts );

// Create an iterator which cumulatively tests whether every iterated value fails a test:
var it = iterCuNoneBy( riter, threshold );

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

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[mdn-iterator-protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterator_protocol

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