@stdlib/utils/nary-function/README.md

Standard utilities.

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# naryFunction

> Create a function that invokes a provided function with a specified number of arguments.

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## Usage

```javascript
var naryFunction = require( '@stdlib/utils/nary-function' );
```

#### naryFunction( fcn, arity\[, thisArg] )

Returns a `function` that invokes a provided function with a specified number of arguments.

```javascript
function sum() {
    var s;
    var i;

    s = 0;
    for ( i = 0; i < arguments.length; i++ ) {
        s += arguments[ i ];
    }
    return s;
}

var fcn = naryFunction( sum, 2 );

var out = fcn( -1, -2, 3 );
// returns -3
```

To set the `this` context when invoking the provided function, provide a `thisArg`.

<!-- eslint-disable no-restricted-syntax -->

```javascript
function Foo() {
    this.scalar = 1;
}

Foo.prototype.sum = function sum() {
    var s;
    var i;

    s = 0;
    for ( i = 0; i < arguments.length; i++ ) {
        s += arguments[ i ] * this.scalar;
    }
    return s;
};

var ctx = {
    'scalar': 3
};

var foo = new Foo();

var fcn = naryFunction( foo.sum, 2, ctx );

var out = fcn( 1, 2, 3 );
// returns 9
```

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## Notes

-   The returned function **always** invokes the wrapped function with a specified number of arguments, even when the returned function is provided fewer arguments. The value for the missing arguments is equal to `undefined`.

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## Examples

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

```javascript
var filledarrayBy = require( '@stdlib/array/filled-by' );
var naryFunction = require( '@stdlib/utils/nary-function' );

function fill( i ) {
    return i;
}

function sum() {
    var s;
    var i;

    s = 0;
    for ( i = 0; i < arguments.length; i++ ) {
        s += arguments[ i ];
    }
    return s;
}

// Create a data array:
var x = filledarrayBy( 10, 'float64', fill );

// Compute cumulative sums...
var f;
var i;
for ( i = 0; i <= x.length; i++ ) {
    f = naryFunction( sum, i );
    console.log( 'sum_%d = %d', i, f.apply( null, x ) );
}
```

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* * *

## See Also

-   <span class="package-name">[`@stdlib/utils/mask-arguments`][@stdlib/utils/mask-arguments]</span><span class="delimiter">: </span><span class="description">create a function that invokes a provided function according to an argument mask.</span>
-   <span class="package-name">[`@stdlib/utils/pick-arguments`][@stdlib/utils/pick-arguments]</span><span class="delimiter">: </span><span class="description">create a function that invokes a provided function with specified arguments.</span>

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[@stdlib/utils/mask-arguments]: https://github.com/stdlib-js/utils/tree/main/mask-arguments

[@stdlib/utils/pick-arguments]: https://github.com/stdlib-js/utils/tree/main/pick-arguments

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