Function vecLength

vecLength(a: Vec2, b?: Vec2): number
Returns the length of a vector
Parameters
- a: Vec2
- b: Vec2 = ...
  If not passed, defaults to [0,0].
Returns number
vector length
Remarks
http://jsperf.com/id-dist-optimization
Example
```
vecLength([0, 0], [4, 3]);   // returns 5
vecLength([4, 3]);           // returns 5
```
- Defined in vector.ts:157