# Point

## Contents

## Construction of a free point

This example shows how to construct a simple, draggable point. It is produced by the following commands:

```
<div id="jxgbox" class="jxgbox" style="width:500px; height:200px;"></div>
<script type="text/javascript">
var board = JXG.JSXGraph.initBoard('jxgbox', {originX: 200, originY: 100, unitX: 50, unitY: 50});
var p = board.createElement('point',[1,1]);
</script>
```

The JavaScript code has to be placed AFTER the div element which will contain the construction. From now on, we will only show the JavaScript code.

## Attributes of a point

### User defined name

Several attributes can be given to change the properties of a point, for example a name.

```
var b2 = JXG.JSXGraph.initBoard('jxgbox2', {originX: 200, originY: 100, unitX: 50, unitY: 50});
var p = b2.createElement('point',[1,1], {name:'X',style:5});
```

This point will be labeled with "X":

### Point styles

The property type of a point can attain the values 0..12. Alternatively you can use these equivalent constants for that:

Constant | Value | Short description |
---|---|---|

JXG.POINT_STYLE_X_SMALL | 0 | Small x |

JXG.POINT_STYLE_X | 1 | Medium x |

JXG.POINT_STYLE_X_BIG | 2 | Big x |

JXG.POINT_STYLE_CIRCLE_TINY | 3 | Tiny circle |

JXG.POINT_STYLE_CIRCLE_SMALL | 4 | Small circle |

JXG.POINT_STYLE_CIRCLE | 5 | Medium circle |

JXG.POINT_STYLE_CIRCLE_BIG | 6 | Big circle |

JXG.POINT_STYLE_SQUARE_SMALL | 7 | Small square |

JXG.POINT_STYLE_SQUARE | 8 | Medium square |

JXG.POINT_STYLE_SQUARE_BIG | 9 | Big square |

JXG.POINT_STYLE_PLUS_SMALL | 10 | Small + |

JXG.POINT_STYLE_PLUS | 11 | Medium + |

JXG.POINT_STYLE_PLUS_BIG | 12 | Big + |

In this examples we use a for loop to create 13 points.

```
var b3 = JXG.JSXGraph.initBoard('jxgbox3', {originX: 40, originY: 100, unitX: 40, unitY: 40});
for (var i=0;i<13;i++) {
var p = b3.createElement('point',[i,0], {name:'P_{'+i+'}', style:i});
}
p.setProperty({fixed:true});
```

### Fixed points

A property of an element may also be set after creating it. In the above example we set the property fixed of the last point, P_12, to true. I.e. the point is no longer draggable.

```
p.setProperty({fixed:true});
```

### Dependent points

A point can depend on any other geometric object. This dependence can be given by using JavaScript functions or terms in GEONExT syntax for coordinates.

#### GEONExT syntax

Here is an example using GEONExT syntax. The point A is draggable. The point B depends on point A: Its y-coordinate is set to 1 and its x-coordinate is set to the x-coordinate of A.

```
var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.createElement('point',[0,0], {name:'A', style:5});
var dep = b.createElement('point',["X(A)",1], {name:'B', style:8});
```

#### JavaScript syntax

Now we do exactly the same with JavaScript syntax.

```
var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 40, originY: 100, unitX: 40, unitY: 40});
var free = b.createElement('point',[0,0], {name:'A', style:5});
var dep = b.createElement('point',[function(){ return free.X();}, 1], {name:'B', style:8});
```

```
var free = b.createElement('point',[0,0], {name:'A', style:5});
```

Then we construct the dependent point "dep".

```
var dep = b.createElement('point',[function(){ return free.X();}, 1], {name:'B', style:8});
```

The first coordinate of "dep" is given as an anonymous function:

```
function(){ return free.X();}
```

This function returns the x-coordinate of the point "free".