# normalizeIndex
> Normalize an index to the interval `[0,max]`.
## Usage
```javascript
var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
```
#### normalizeIndex( idx, max )
Normalizes an index to the interval `[0,max]`.
```javascript
var idx = normalizeIndex( 2, 10 );
// returns 2
idx = normalizeIndex( -5, 10 );
// returns 6
```
If provided an out-of-bounds index, the function returns `-1`.
```javascript
var idx = normalizeIndex( 15, 10 );
// returns -1
idx = normalizeIndex( -15, 10 );
// returns -1
```
## Notes
- During normalization, a negative index is converted to a nonnegative index according to `max + idx + 1`. If, after normalization, the resolved index is still negative, the value is considered out-of-bounds.
## Examples
```javascript
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var normalizeIndex = require( '@stdlib/ndarray/base/normalize-index' );
var idx;
var out;
var i;
for ( i = 0; i < 100; i++ ) {
idx = discreteUniform( -20, 20 );
out = normalizeIndex( idx, 15 );
console.log( '%d => [%d,%d] => %d', idx, 0, 15, out );
}
```