@stdlib/string/base/starts-with/README.md

String manipulation functions.

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# startsWith

> Test if a string starts with the characters of another string.

<section class="intro">

</section>

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<section class="usage">

## Usage

```javascript
var startsWith = require( '@stdlib/string/base/starts-with' );
```

#### startsWith( str, search, position )

Tests if a string starts with the characters of another string.

```javascript
var str = 'To be, or not to be, that is the question.';

var bool = startsWith( str, 'To be', 0 );
// returns true

bool = startsWith( str, 'to be', 0 );
// returns false
```

To search from a specific character index, provide a `position` value (zero-based). If provided a negative `position`, the start index is determined relative to the string end (i.e., `pos = str.length + position`).

```javascript
var str = 'Remember the story I used to tell you when you were a boy?';

var bool = startsWith( str, 'the story', 0 );
// returns false

bool = startsWith( str, 'the story', 9 );
// returns true

bool = startsWith( str, 'you', -15 );
// returns true
```

If provided an empty `search` string, the function **always** returns `true`.

```javascript
var str = 'beep boop';

var bool = startsWith( str, '', 0 );
// returns true
```

</section>

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<section class="notes">

## Notes

-   This function differs from [`String.prototype.startsWith`][mdn-string-startswith] in the following ways:

    -   The function assumes string values for the first and second arguments and assumes that the `position` argument is an integer value.
    -   The function does **not** clamp negative `position` values. Instead, when provided a negative `position`, the function resolves the starting search position relative to the end of the string.
    -   Except when provided an empty `search` string, the function **always** returns `false` if a `position` resolves to a starting search position which exceeds the bounds of the input string.

</section>

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<section class="examples">

## Examples

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

```javascript
var startsWith = require( '@stdlib/string/base/starts-with' );

var str = 'Fair is foul, and foul is fair, hover through fog and filthy air';

var bool = startsWith( str, 'Fair', 0 );
// returns true

bool = startsWith( str, 'fair', 0 );
// returns false

bool = startsWith( str, 'foul', 8 );
// returns true

bool = startsWith( str, 'filthy', -10 );
// returns true
```

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<section class="links">

[mdn-string-startswith]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/startsWith

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