/**
Split a string on the first occurrence of a given separator.
@param string - The string to split.
@param separator - The separator to split on.
@example
```
import splitOnFirst = require('split-on-first');
splitOnFirst('a-b-c', '-');
//=> ['a', 'b-c']
splitOnFirst('key:value:value2', ':');
//=> ['key', 'value:value2']
splitOnFirst('a---b---c', '---');
//=> ['a', 'b---c']
splitOnFirst('a-b-c', '+');
//=> ['a-b-c']
```
*/
declare function splitOnFirst(
string: string,
separator: string
): [string, string?];
export = splitOnFirst;