startsWith

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

Usage

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

startsWith( str, search, position )

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

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).

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.

var str = 'beep boop';

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

Notes

This function differs from String.prototype.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.

Examples

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